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0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /* RxRPC packet reception
0003  *
0004  * Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
0005  * Written by David Howells (dhowells@redhat.com)
0006  */
0007 
0008 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0009 
0010 #include <linux/module.h>
0011 #include <linux/net.h>
0012 #include <linux/skbuff.h>
0013 #include <linux/errqueue.h>
0014 #include <linux/udp.h>
0015 #include <linux/in.h>
0016 #include <linux/in6.h>
0017 #include <linux/icmp.h>
0018 #include <linux/gfp.h>
0019 #include <net/sock.h>
0020 #include <net/af_rxrpc.h>
0021 #include <net/ip.h>
0022 #include <net/udp.h>
0023 #include <net/net_namespace.h>
0024 #include "ar-internal.h"
0025 
0026 static void rxrpc_proto_abort(const char *why,
0027                   struct rxrpc_call *call, rxrpc_seq_t seq)
0028 {
0029     if (rxrpc_abort_call(why, call, seq, RX_PROTOCOL_ERROR, -EBADMSG)) {
0030         set_bit(RXRPC_CALL_EV_ABORT, &call->events);
0031         rxrpc_queue_call(call);
0032     }
0033 }
0034 
0035 /*
0036  * Do TCP-style congestion management [RFC 5681].
0037  */
0038 static void rxrpc_congestion_management(struct rxrpc_call *call,
0039                     struct sk_buff *skb,
0040                     struct rxrpc_ack_summary *summary,
0041                     rxrpc_serial_t acked_serial)
0042 {
0043     enum rxrpc_congest_change change = rxrpc_cong_no_change;
0044     unsigned int cumulative_acks = call->cong_cumul_acks;
0045     unsigned int cwnd = call->cong_cwnd;
0046     bool resend = false;
0047 
0048     summary->flight_size =
0049         (call->tx_top - call->tx_hard_ack) - summary->nr_acks;
0050 
0051     if (test_and_clear_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags)) {
0052         summary->retrans_timeo = true;
0053         call->cong_ssthresh = max_t(unsigned int,
0054                         summary->flight_size / 2, 2);
0055         cwnd = 1;
0056         if (cwnd >= call->cong_ssthresh &&
0057             call->cong_mode == RXRPC_CALL_SLOW_START) {
0058             call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
0059             call->cong_tstamp = skb->tstamp;
0060             cumulative_acks = 0;
0061         }
0062     }
0063 
0064     cumulative_acks += summary->nr_new_acks;
0065     cumulative_acks += summary->nr_rot_new_acks;
0066     if (cumulative_acks > 255)
0067         cumulative_acks = 255;
0068 
0069     summary->mode = call->cong_mode;
0070     summary->cwnd = call->cong_cwnd;
0071     summary->ssthresh = call->cong_ssthresh;
0072     summary->cumulative_acks = cumulative_acks;
0073     summary->dup_acks = call->cong_dup_acks;
0074 
0075     switch (call->cong_mode) {
0076     case RXRPC_CALL_SLOW_START:
0077         if (summary->nr_nacks > 0)
0078             goto packet_loss_detected;
0079         if (summary->cumulative_acks > 0)
0080             cwnd += 1;
0081         if (cwnd >= call->cong_ssthresh) {
0082             call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
0083             call->cong_tstamp = skb->tstamp;
0084         }
0085         goto out;
0086 
0087     case RXRPC_CALL_CONGEST_AVOIDANCE:
0088         if (summary->nr_nacks > 0)
0089             goto packet_loss_detected;
0090 
0091         /* We analyse the number of packets that get ACK'd per RTT
0092          * period and increase the window if we managed to fill it.
0093          */
0094         if (call->peer->rtt_count == 0)
0095             goto out;
0096         if (ktime_before(skb->tstamp,
0097                  ktime_add_us(call->cong_tstamp,
0098                           call->peer->srtt_us >> 3)))
0099             goto out_no_clear_ca;
0100         change = rxrpc_cong_rtt_window_end;
0101         call->cong_tstamp = skb->tstamp;
0102         if (cumulative_acks >= cwnd)
0103             cwnd++;
0104         goto out;
0105 
0106     case RXRPC_CALL_PACKET_LOSS:
0107         if (summary->nr_nacks == 0)
0108             goto resume_normality;
0109 
0110         if (summary->new_low_nack) {
0111             change = rxrpc_cong_new_low_nack;
0112             call->cong_dup_acks = 1;
0113             if (call->cong_extra > 1)
0114                 call->cong_extra = 1;
0115             goto send_extra_data;
0116         }
0117 
0118         call->cong_dup_acks++;
0119         if (call->cong_dup_acks < 3)
0120             goto send_extra_data;
0121 
0122         change = rxrpc_cong_begin_retransmission;
0123         call->cong_mode = RXRPC_CALL_FAST_RETRANSMIT;
0124         call->cong_ssthresh = max_t(unsigned int,
0125                         summary->flight_size / 2, 2);
0126         cwnd = call->cong_ssthresh + 3;
0127         call->cong_extra = 0;
0128         call->cong_dup_acks = 0;
0129         resend = true;
0130         goto out;
0131 
0132     case RXRPC_CALL_FAST_RETRANSMIT:
0133         if (!summary->new_low_nack) {
0134             if (summary->nr_new_acks == 0)
0135                 cwnd += 1;
0136             call->cong_dup_acks++;
0137             if (call->cong_dup_acks == 2) {
0138                 change = rxrpc_cong_retransmit_again;
0139                 call->cong_dup_acks = 0;
0140                 resend = true;
0141             }
0142         } else {
0143             change = rxrpc_cong_progress;
0144             cwnd = call->cong_ssthresh;
0145             if (summary->nr_nacks == 0)
0146                 goto resume_normality;
0147         }
0148         goto out;
0149 
0150     default:
0151         BUG();
0152         goto out;
0153     }
0154 
0155 resume_normality:
0156     change = rxrpc_cong_cleared_nacks;
0157     call->cong_dup_acks = 0;
0158     call->cong_extra = 0;
0159     call->cong_tstamp = skb->tstamp;
0160     if (cwnd < call->cong_ssthresh)
0161         call->cong_mode = RXRPC_CALL_SLOW_START;
0162     else
0163         call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
0164 out:
0165     cumulative_acks = 0;
0166 out_no_clear_ca:
0167     if (cwnd >= RXRPC_RXTX_BUFF_SIZE - 1)
0168         cwnd = RXRPC_RXTX_BUFF_SIZE - 1;
0169     call->cong_cwnd = cwnd;
0170     call->cong_cumul_acks = cumulative_acks;
0171     trace_rxrpc_congest(call, summary, acked_serial, change);
0172     if (resend && !test_and_set_bit(RXRPC_CALL_EV_RESEND, &call->events))
0173         rxrpc_queue_call(call);
0174     return;
0175 
0176 packet_loss_detected:
0177     change = rxrpc_cong_saw_nack;
0178     call->cong_mode = RXRPC_CALL_PACKET_LOSS;
0179     call->cong_dup_acks = 0;
0180     goto send_extra_data;
0181 
0182 send_extra_data:
0183     /* Send some previously unsent DATA if we have some to advance the ACK
0184      * state.
0185      */
0186     if (call->rxtx_annotations[call->tx_top & RXRPC_RXTX_BUFF_MASK] &
0187         RXRPC_TX_ANNO_LAST ||
0188         summary->nr_acks != call->tx_top - call->tx_hard_ack) {
0189         call->cong_extra++;
0190         wake_up(&call->waitq);
0191     }
0192     goto out_no_clear_ca;
0193 }
0194 
0195 /*
0196  * Apply a hard ACK by advancing the Tx window.
0197  */
0198 static bool rxrpc_rotate_tx_window(struct rxrpc_call *call, rxrpc_seq_t to,
0199                    struct rxrpc_ack_summary *summary)
0200 {
0201     struct sk_buff *skb, *list = NULL;
0202     bool rot_last = false;
0203     int ix;
0204     u8 annotation;
0205 
0206     if (call->acks_lowest_nak == call->tx_hard_ack) {
0207         call->acks_lowest_nak = to;
0208     } else if (before_eq(call->acks_lowest_nak, to)) {
0209         summary->new_low_nack = true;
0210         call->acks_lowest_nak = to;
0211     }
0212 
0213     spin_lock(&call->lock);
0214 
0215     while (before(call->tx_hard_ack, to)) {
0216         call->tx_hard_ack++;
0217         ix = call->tx_hard_ack & RXRPC_RXTX_BUFF_MASK;
0218         skb = call->rxtx_buffer[ix];
0219         annotation = call->rxtx_annotations[ix];
0220         rxrpc_see_skb(skb, rxrpc_skb_rotated);
0221         call->rxtx_buffer[ix] = NULL;
0222         call->rxtx_annotations[ix] = 0;
0223         skb->next = list;
0224         list = skb;
0225 
0226         if (annotation & RXRPC_TX_ANNO_LAST) {
0227             set_bit(RXRPC_CALL_TX_LAST, &call->flags);
0228             rot_last = true;
0229         }
0230         if ((annotation & RXRPC_TX_ANNO_MASK) != RXRPC_TX_ANNO_ACK)
0231             summary->nr_rot_new_acks++;
0232     }
0233 
0234     spin_unlock(&call->lock);
0235 
0236     trace_rxrpc_transmit(call, (rot_last ?
0237                     rxrpc_transmit_rotate_last :
0238                     rxrpc_transmit_rotate));
0239     wake_up(&call->waitq);
0240 
0241     while (list) {
0242         skb = list;
0243         list = skb->next;
0244         skb_mark_not_on_list(skb);
0245         rxrpc_free_skb(skb, rxrpc_skb_freed);
0246     }
0247 
0248     return rot_last;
0249 }
0250 
0251 /*
0252  * End the transmission phase of a call.
0253  *
0254  * This occurs when we get an ACKALL packet, the first DATA packet of a reply,
0255  * or a final ACK packet.
0256  */
0257 static bool rxrpc_end_tx_phase(struct rxrpc_call *call, bool reply_begun,
0258                    const char *abort_why)
0259 {
0260     unsigned int state;
0261 
0262     ASSERT(test_bit(RXRPC_CALL_TX_LAST, &call->flags));
0263 
0264     write_lock(&call->state_lock);
0265 
0266     state = call->state;
0267     switch (state) {
0268     case RXRPC_CALL_CLIENT_SEND_REQUEST:
0269     case RXRPC_CALL_CLIENT_AWAIT_REPLY:
0270         if (reply_begun)
0271             call->state = state = RXRPC_CALL_CLIENT_RECV_REPLY;
0272         else
0273             call->state = state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
0274         break;
0275 
0276     case RXRPC_CALL_SERVER_AWAIT_ACK:
0277         __rxrpc_call_completed(call);
0278         state = call->state;
0279         break;
0280 
0281     default:
0282         goto bad_state;
0283     }
0284 
0285     write_unlock(&call->state_lock);
0286     if (state == RXRPC_CALL_CLIENT_AWAIT_REPLY)
0287         trace_rxrpc_transmit(call, rxrpc_transmit_await_reply);
0288     else
0289         trace_rxrpc_transmit(call, rxrpc_transmit_end);
0290     _leave(" = ok");
0291     return true;
0292 
0293 bad_state:
0294     write_unlock(&call->state_lock);
0295     kdebug("end_tx %s", rxrpc_call_states[call->state]);
0296     rxrpc_proto_abort(abort_why, call, call->tx_top);
0297     return false;
0298 }
0299 
0300 /*
0301  * Begin the reply reception phase of a call.
0302  */
0303 static bool rxrpc_receiving_reply(struct rxrpc_call *call)
0304 {
0305     struct rxrpc_ack_summary summary = { 0 };
0306     unsigned long now, timo;
0307     rxrpc_seq_t top = READ_ONCE(call->tx_top);
0308 
0309     if (call->ackr_reason) {
0310         spin_lock_bh(&call->lock);
0311         call->ackr_reason = 0;
0312         spin_unlock_bh(&call->lock);
0313         now = jiffies;
0314         timo = now + MAX_JIFFY_OFFSET;
0315         WRITE_ONCE(call->resend_at, timo);
0316         WRITE_ONCE(call->ack_at, timo);
0317         trace_rxrpc_timer(call, rxrpc_timer_init_for_reply, now);
0318     }
0319 
0320     if (!test_bit(RXRPC_CALL_TX_LAST, &call->flags)) {
0321         if (!rxrpc_rotate_tx_window(call, top, &summary)) {
0322             rxrpc_proto_abort("TXL", call, top);
0323             return false;
0324         }
0325     }
0326     if (!rxrpc_end_tx_phase(call, true, "ETD"))
0327         return false;
0328     call->tx_phase = false;
0329     return true;
0330 }
0331 
0332 /*
0333  * Scan a data packet to validate its structure and to work out how many
0334  * subpackets it contains.
0335  *
0336  * A jumbo packet is a collection of consecutive packets glued together with
0337  * little headers between that indicate how to change the initial header for
0338  * each subpacket.
0339  *
0340  * RXRPC_JUMBO_PACKET must be set on all but the last subpacket - and all but
0341  * the last are RXRPC_JUMBO_DATALEN in size.  The last subpacket may be of any
0342  * size.
0343  */
0344 static bool rxrpc_validate_data(struct sk_buff *skb)
0345 {
0346     struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
0347     unsigned int offset = sizeof(struct rxrpc_wire_header);
0348     unsigned int len = skb->len;
0349     u8 flags = sp->hdr.flags;
0350 
0351     for (;;) {
0352         if (flags & RXRPC_REQUEST_ACK)
0353             __set_bit(sp->nr_subpackets, sp->rx_req_ack);
0354         sp->nr_subpackets++;
0355 
0356         if (!(flags & RXRPC_JUMBO_PACKET))
0357             break;
0358 
0359         if (len - offset < RXRPC_JUMBO_SUBPKTLEN)
0360             goto protocol_error;
0361         if (flags & RXRPC_LAST_PACKET)
0362             goto protocol_error;
0363         offset += RXRPC_JUMBO_DATALEN;
0364         if (skb_copy_bits(skb, offset, &flags, 1) < 0)
0365             goto protocol_error;
0366         offset += sizeof(struct rxrpc_jumbo_header);
0367     }
0368 
0369     if (flags & RXRPC_LAST_PACKET)
0370         sp->rx_flags |= RXRPC_SKB_INCL_LAST;
0371     return true;
0372 
0373 protocol_error:
0374     return false;
0375 }
0376 
0377 /*
0378  * Handle reception of a duplicate packet.
0379  *
0380  * We have to take care to avoid an attack here whereby we're given a series of
0381  * jumbograms, each with a sequence number one before the preceding one and
0382  * filled up to maximum UDP size.  If they never send us the first packet in
0383  * the sequence, they can cause us to have to hold on to around 2MiB of kernel
0384  * space until the call times out.
0385  *
0386  * We limit the space usage by only accepting three duplicate jumbo packets per
0387  * call.  After that, we tell the other side we're no longer accepting jumbos
0388  * (that information is encoded in the ACK packet).
0389  */
0390 static void rxrpc_input_dup_data(struct rxrpc_call *call, rxrpc_seq_t seq,
0391                  bool is_jumbo, bool *_jumbo_bad)
0392 {
0393     /* Discard normal packets that are duplicates. */
0394     if (is_jumbo)
0395         return;
0396 
0397     /* Skip jumbo subpackets that are duplicates.  When we've had three or
0398      * more partially duplicate jumbo packets, we refuse to take any more
0399      * jumbos for this call.
0400      */
0401     if (!*_jumbo_bad) {
0402         call->nr_jumbo_bad++;
0403         *_jumbo_bad = true;
0404     }
0405 }
0406 
0407 /*
0408  * Process a DATA packet, adding the packet to the Rx ring.  The caller's
0409  * packet ref must be passed on or discarded.
0410  */
0411 static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb)
0412 {
0413     struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
0414     enum rxrpc_call_state state;
0415     unsigned int j, nr_subpackets, nr_unacked = 0;
0416     rxrpc_serial_t serial = sp->hdr.serial, ack_serial = serial;
0417     rxrpc_seq_t seq0 = sp->hdr.seq, hard_ack;
0418     bool immediate_ack = false, jumbo_bad = false;
0419     u8 ack = 0;
0420 
0421     _enter("{%u,%u},{%u,%u}",
0422            call->rx_hard_ack, call->rx_top, skb->len, seq0);
0423 
0424     _proto("Rx DATA %%%u { #%u f=%02x n=%u }",
0425            sp->hdr.serial, seq0, sp->hdr.flags, sp->nr_subpackets);
0426 
0427     state = READ_ONCE(call->state);
0428     if (state >= RXRPC_CALL_COMPLETE) {
0429         rxrpc_free_skb(skb, rxrpc_skb_freed);
0430         return;
0431     }
0432 
0433     if (state == RXRPC_CALL_SERVER_RECV_REQUEST) {
0434         unsigned long timo = READ_ONCE(call->next_req_timo);
0435         unsigned long now, expect_req_by;
0436 
0437         if (timo) {
0438             now = jiffies;
0439             expect_req_by = now + timo;
0440             WRITE_ONCE(call->expect_req_by, expect_req_by);
0441             rxrpc_reduce_call_timer(call, expect_req_by, now,
0442                         rxrpc_timer_set_for_idle);
0443         }
0444     }
0445 
0446     spin_lock(&call->input_lock);
0447 
0448     /* Received data implicitly ACKs all of the request packets we sent
0449      * when we're acting as a client.
0450      */
0451     if ((state == RXRPC_CALL_CLIENT_SEND_REQUEST ||
0452          state == RXRPC_CALL_CLIENT_AWAIT_REPLY) &&
0453         !rxrpc_receiving_reply(call))
0454         goto unlock;
0455 
0456     hard_ack = READ_ONCE(call->rx_hard_ack);
0457 
0458     nr_subpackets = sp->nr_subpackets;
0459     if (nr_subpackets > 1) {
0460         if (call->nr_jumbo_bad > 3) {
0461             ack = RXRPC_ACK_NOSPACE;
0462             ack_serial = serial;
0463             goto ack;
0464         }
0465     }
0466 
0467     for (j = 0; j < nr_subpackets; j++) {
0468         rxrpc_serial_t serial = sp->hdr.serial + j;
0469         rxrpc_seq_t seq = seq0 + j;
0470         unsigned int ix = seq & RXRPC_RXTX_BUFF_MASK;
0471         bool terminal = (j == nr_subpackets - 1);
0472         bool last = terminal && (sp->rx_flags & RXRPC_SKB_INCL_LAST);
0473         u8 flags, annotation = j;
0474 
0475         _proto("Rx DATA+%u %%%u { #%x t=%u l=%u }",
0476              j, serial, seq, terminal, last);
0477 
0478         if (last) {
0479             if (test_bit(RXRPC_CALL_RX_LAST, &call->flags) &&
0480                 seq != call->rx_top) {
0481                 rxrpc_proto_abort("LSN", call, seq);
0482                 goto unlock;
0483             }
0484         } else {
0485             if (test_bit(RXRPC_CALL_RX_LAST, &call->flags) &&
0486                 after_eq(seq, call->rx_top)) {
0487                 rxrpc_proto_abort("LSA", call, seq);
0488                 goto unlock;
0489             }
0490         }
0491 
0492         flags = 0;
0493         if (last)
0494             flags |= RXRPC_LAST_PACKET;
0495         if (!terminal)
0496             flags |= RXRPC_JUMBO_PACKET;
0497         if (test_bit(j, sp->rx_req_ack))
0498             flags |= RXRPC_REQUEST_ACK;
0499         trace_rxrpc_rx_data(call->debug_id, seq, serial, flags, annotation);
0500 
0501         if (before_eq(seq, hard_ack)) {
0502             ack = RXRPC_ACK_DUPLICATE;
0503             ack_serial = serial;
0504             continue;
0505         }
0506 
0507         if (call->rxtx_buffer[ix]) {
0508             rxrpc_input_dup_data(call, seq, nr_subpackets > 1,
0509                          &jumbo_bad);
0510             if (ack != RXRPC_ACK_DUPLICATE) {
0511                 ack = RXRPC_ACK_DUPLICATE;
0512                 ack_serial = serial;
0513             }
0514             immediate_ack = true;
0515             continue;
0516         }
0517 
0518         if (after(seq, hard_ack + call->rx_winsize)) {
0519             ack = RXRPC_ACK_EXCEEDS_WINDOW;
0520             ack_serial = serial;
0521             if (flags & RXRPC_JUMBO_PACKET) {
0522                 if (!jumbo_bad) {
0523                     call->nr_jumbo_bad++;
0524                     jumbo_bad = true;
0525                 }
0526             }
0527 
0528             goto ack;
0529         }
0530 
0531         if (flags & RXRPC_REQUEST_ACK && !ack) {
0532             ack = RXRPC_ACK_REQUESTED;
0533             ack_serial = serial;
0534         }
0535 
0536         if (after(seq0, call->ackr_highest_seq))
0537             call->ackr_highest_seq = seq0;
0538 
0539         /* Queue the packet.  We use a couple of memory barriers here as need
0540          * to make sure that rx_top is perceived to be set after the buffer
0541          * pointer and that the buffer pointer is set after the annotation and
0542          * the skb data.
0543          *
0544          * Barriers against rxrpc_recvmsg_data() and rxrpc_rotate_rx_window()
0545          * and also rxrpc_fill_out_ack().
0546          */
0547         if (!terminal)
0548             rxrpc_get_skb(skb, rxrpc_skb_got);
0549         call->rxtx_annotations[ix] = annotation;
0550         smp_wmb();
0551         call->rxtx_buffer[ix] = skb;
0552         if (after(seq, call->rx_top)) {
0553             smp_store_release(&call->rx_top, seq);
0554         } else if (before(seq, call->rx_top)) {
0555             /* Send an immediate ACK if we fill in a hole */
0556             if (!ack) {
0557                 ack = RXRPC_ACK_DELAY;
0558                 ack_serial = serial;
0559             }
0560             immediate_ack = true;
0561         }
0562 
0563         if (terminal) {
0564             /* From this point on, we're not allowed to touch the
0565              * packet any longer as its ref now belongs to the Rx
0566              * ring.
0567              */
0568             skb = NULL;
0569             sp = NULL;
0570         }
0571 
0572         nr_unacked++;
0573 
0574         if (last) {
0575             set_bit(RXRPC_CALL_RX_LAST, &call->flags);
0576             if (!ack) {
0577                 ack = RXRPC_ACK_DELAY;
0578                 ack_serial = serial;
0579             }
0580             trace_rxrpc_receive(call, rxrpc_receive_queue_last, serial, seq);
0581         } else {
0582             trace_rxrpc_receive(call, rxrpc_receive_queue, serial, seq);
0583         }
0584 
0585         if (after_eq(seq, call->rx_expect_next)) {
0586             if (after(seq, call->rx_expect_next)) {
0587                 _net("OOS %u > %u", seq, call->rx_expect_next);
0588                 ack = RXRPC_ACK_OUT_OF_SEQUENCE;
0589                 ack_serial = serial;
0590             }
0591             call->rx_expect_next = seq + 1;
0592         }
0593         if (!ack)
0594             ack_serial = serial;
0595     }
0596 
0597 ack:
0598     if (atomic_add_return(nr_unacked, &call->ackr_nr_unacked) > 2 && !ack)
0599         ack = RXRPC_ACK_IDLE;
0600 
0601     if (ack)
0602         rxrpc_propose_ACK(call, ack, ack_serial,
0603                   immediate_ack, true,
0604                   rxrpc_propose_ack_input_data);
0605     else
0606         rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, serial,
0607                   false, true,
0608                   rxrpc_propose_ack_input_data);
0609 
0610     trace_rxrpc_notify_socket(call->debug_id, serial);
0611     rxrpc_notify_socket(call);
0612 
0613 unlock:
0614     spin_unlock(&call->input_lock);
0615     rxrpc_free_skb(skb, rxrpc_skb_freed);
0616     _leave(" [queued]");
0617 }
0618 
0619 /*
0620  * See if there's a cached RTT probe to complete.
0621  */
0622 static void rxrpc_complete_rtt_probe(struct rxrpc_call *call,
0623                      ktime_t resp_time,
0624                      rxrpc_serial_t acked_serial,
0625                      rxrpc_serial_t ack_serial,
0626                      enum rxrpc_rtt_rx_trace type)
0627 {
0628     rxrpc_serial_t orig_serial;
0629     unsigned long avail;
0630     ktime_t sent_at;
0631     bool matched = false;
0632     int i;
0633 
0634     avail = READ_ONCE(call->rtt_avail);
0635     smp_rmb(); /* Read avail bits before accessing data. */
0636 
0637     for (i = 0; i < ARRAY_SIZE(call->rtt_serial); i++) {
0638         if (!test_bit(i + RXRPC_CALL_RTT_PEND_SHIFT, &avail))
0639             continue;
0640 
0641         sent_at = call->rtt_sent_at[i];
0642         orig_serial = call->rtt_serial[i];
0643 
0644         if (orig_serial == acked_serial) {
0645             clear_bit(i + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
0646             smp_mb(); /* Read data before setting avail bit */
0647             set_bit(i, &call->rtt_avail);
0648             if (type != rxrpc_rtt_rx_cancel)
0649                 rxrpc_peer_add_rtt(call, type, i, acked_serial, ack_serial,
0650                            sent_at, resp_time);
0651             else
0652                 trace_rxrpc_rtt_rx(call, rxrpc_rtt_rx_cancel, i,
0653                            orig_serial, acked_serial, 0, 0);
0654             matched = true;
0655         }
0656 
0657         /* If a later serial is being acked, then mark this slot as
0658          * being available.
0659          */
0660         if (after(acked_serial, orig_serial)) {
0661             trace_rxrpc_rtt_rx(call, rxrpc_rtt_rx_obsolete, i,
0662                        orig_serial, acked_serial, 0, 0);
0663             clear_bit(i + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
0664             smp_wmb();
0665             set_bit(i, &call->rtt_avail);
0666         }
0667     }
0668 
0669     if (!matched)
0670         trace_rxrpc_rtt_rx(call, rxrpc_rtt_rx_lost, 9, 0, acked_serial, 0, 0);
0671 }
0672 
0673 /*
0674  * Process the response to a ping that we sent to find out if we lost an ACK.
0675  *
0676  * If we got back a ping response that indicates a lower tx_top than what we
0677  * had at the time of the ping transmission, we adjudge all the DATA packets
0678  * sent between the response tx_top and the ping-time tx_top to have been lost.
0679  */
0680 static void rxrpc_input_check_for_lost_ack(struct rxrpc_call *call)
0681 {
0682     rxrpc_seq_t top, bottom, seq;
0683     bool resend = false;
0684 
0685     spin_lock_bh(&call->lock);
0686 
0687     bottom = call->tx_hard_ack + 1;
0688     top = call->acks_lost_top;
0689     if (before(bottom, top)) {
0690         for (seq = bottom; before_eq(seq, top); seq++) {
0691             int ix = seq & RXRPC_RXTX_BUFF_MASK;
0692             u8 annotation = call->rxtx_annotations[ix];
0693             u8 anno_type = annotation & RXRPC_TX_ANNO_MASK;
0694 
0695             if (anno_type != RXRPC_TX_ANNO_UNACK)
0696                 continue;
0697             annotation &= ~RXRPC_TX_ANNO_MASK;
0698             annotation |= RXRPC_TX_ANNO_RETRANS;
0699             call->rxtx_annotations[ix] = annotation;
0700             resend = true;
0701         }
0702     }
0703 
0704     spin_unlock_bh(&call->lock);
0705 
0706     if (resend && !test_and_set_bit(RXRPC_CALL_EV_RESEND, &call->events))
0707         rxrpc_queue_call(call);
0708 }
0709 
0710 /*
0711  * Process a ping response.
0712  */
0713 static void rxrpc_input_ping_response(struct rxrpc_call *call,
0714                       ktime_t resp_time,
0715                       rxrpc_serial_t acked_serial,
0716                       rxrpc_serial_t ack_serial)
0717 {
0718     if (acked_serial == call->acks_lost_ping)
0719         rxrpc_input_check_for_lost_ack(call);
0720 }
0721 
0722 /*
0723  * Process the extra information that may be appended to an ACK packet
0724  */
0725 static void rxrpc_input_ackinfo(struct rxrpc_call *call, struct sk_buff *skb,
0726                 struct rxrpc_ackinfo *ackinfo)
0727 {
0728     struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
0729     struct rxrpc_peer *peer;
0730     unsigned int mtu;
0731     bool wake = false;
0732     u32 rwind = ntohl(ackinfo->rwind);
0733 
0734     _proto("Rx ACK %%%u Info { rx=%u max=%u rwin=%u jm=%u }",
0735            sp->hdr.serial,
0736            ntohl(ackinfo->rxMTU), ntohl(ackinfo->maxMTU),
0737            rwind, ntohl(ackinfo->jumbo_max));
0738 
0739     if (rwind > RXRPC_RXTX_BUFF_SIZE - 1)
0740         rwind = RXRPC_RXTX_BUFF_SIZE - 1;
0741     if (call->tx_winsize != rwind) {
0742         if (rwind > call->tx_winsize)
0743             wake = true;
0744         trace_rxrpc_rx_rwind_change(call, sp->hdr.serial, rwind, wake);
0745         call->tx_winsize = rwind;
0746     }
0747 
0748     if (call->cong_ssthresh > rwind)
0749         call->cong_ssthresh = rwind;
0750 
0751     mtu = min(ntohl(ackinfo->rxMTU), ntohl(ackinfo->maxMTU));
0752 
0753     peer = call->peer;
0754     if (mtu < peer->maxdata) {
0755         spin_lock_bh(&peer->lock);
0756         peer->maxdata = mtu;
0757         peer->mtu = mtu + peer->hdrsize;
0758         spin_unlock_bh(&peer->lock);
0759         _net("Net MTU %u (maxdata %u)", peer->mtu, peer->maxdata);
0760     }
0761 
0762     if (wake)
0763         wake_up(&call->waitq);
0764 }
0765 
0766 /*
0767  * Process individual soft ACKs.
0768  *
0769  * Each ACK in the array corresponds to one packet and can be either an ACK or
0770  * a NAK.  If we get find an explicitly NAK'd packet we resend immediately;
0771  * packets that lie beyond the end of the ACK list are scheduled for resend by
0772  * the timer on the basis that the peer might just not have processed them at
0773  * the time the ACK was sent.
0774  */
0775 static void rxrpc_input_soft_acks(struct rxrpc_call *call, u8 *acks,
0776                   rxrpc_seq_t seq, int nr_acks,
0777                   struct rxrpc_ack_summary *summary)
0778 {
0779     int ix;
0780     u8 annotation, anno_type;
0781 
0782     for (; nr_acks > 0; nr_acks--, seq++) {
0783         ix = seq & RXRPC_RXTX_BUFF_MASK;
0784         annotation = call->rxtx_annotations[ix];
0785         anno_type = annotation & RXRPC_TX_ANNO_MASK;
0786         annotation &= ~RXRPC_TX_ANNO_MASK;
0787         switch (*acks++) {
0788         case RXRPC_ACK_TYPE_ACK:
0789             summary->nr_acks++;
0790             if (anno_type == RXRPC_TX_ANNO_ACK)
0791                 continue;
0792             summary->nr_new_acks++;
0793             call->rxtx_annotations[ix] =
0794                 RXRPC_TX_ANNO_ACK | annotation;
0795             break;
0796         case RXRPC_ACK_TYPE_NACK:
0797             if (!summary->nr_nacks &&
0798                 call->acks_lowest_nak != seq) {
0799                 call->acks_lowest_nak = seq;
0800                 summary->new_low_nack = true;
0801             }
0802             summary->nr_nacks++;
0803             if (anno_type == RXRPC_TX_ANNO_NAK)
0804                 continue;
0805             summary->nr_new_nacks++;
0806             if (anno_type == RXRPC_TX_ANNO_RETRANS)
0807                 continue;
0808             call->rxtx_annotations[ix] =
0809                 RXRPC_TX_ANNO_NAK | annotation;
0810             break;
0811         default:
0812             return rxrpc_proto_abort("SFT", call, 0);
0813         }
0814     }
0815 }
0816 
0817 /*
0818  * Return true if the ACK is valid - ie. it doesn't appear to have regressed
0819  * with respect to the ack state conveyed by preceding ACKs.
0820  */
0821 static bool rxrpc_is_ack_valid(struct rxrpc_call *call,
0822                    rxrpc_seq_t first_pkt, rxrpc_seq_t prev_pkt)
0823 {
0824     rxrpc_seq_t base = READ_ONCE(call->acks_first_seq);
0825 
0826     if (after(first_pkt, base))
0827         return true; /* The window advanced */
0828 
0829     if (before(first_pkt, base))
0830         return false; /* firstPacket regressed */
0831 
0832     if (after_eq(prev_pkt, call->acks_prev_seq))
0833         return true; /* previousPacket hasn't regressed. */
0834 
0835     /* Some rx implementations put a serial number in previousPacket. */
0836     if (after_eq(prev_pkt, base + call->tx_winsize))
0837         return false;
0838     return true;
0839 }
0840 
0841 /*
0842  * Process an ACK packet.
0843  *
0844  * ack.firstPacket is the sequence number of the first soft-ACK'd/NAK'd packet
0845  * in the ACK array.  Anything before that is hard-ACK'd and may be discarded.
0846  *
0847  * A hard-ACK means that a packet has been processed and may be discarded; a
0848  * soft-ACK means that the packet may be discarded and retransmission
0849  * requested.  A phase is complete when all packets are hard-ACK'd.
0850  */
0851 static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
0852 {
0853     struct rxrpc_ack_summary summary = { 0 };
0854     struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
0855     union {
0856         struct rxrpc_ackpacket ack;
0857         struct rxrpc_ackinfo info;
0858         u8 acks[RXRPC_MAXACKS];
0859     } buf;
0860     rxrpc_serial_t ack_serial, acked_serial;
0861     rxrpc_seq_t first_soft_ack, hard_ack, prev_pkt;
0862     int nr_acks, offset, ioffset;
0863 
0864     _enter("");
0865 
0866     offset = sizeof(struct rxrpc_wire_header);
0867     if (skb_copy_bits(skb, offset, &buf.ack, sizeof(buf.ack)) < 0) {
0868         _debug("extraction failure");
0869         return rxrpc_proto_abort("XAK", call, 0);
0870     }
0871     offset += sizeof(buf.ack);
0872 
0873     ack_serial = sp->hdr.serial;
0874     acked_serial = ntohl(buf.ack.serial);
0875     first_soft_ack = ntohl(buf.ack.firstPacket);
0876     prev_pkt = ntohl(buf.ack.previousPacket);
0877     hard_ack = first_soft_ack - 1;
0878     nr_acks = buf.ack.nAcks;
0879     summary.ack_reason = (buf.ack.reason < RXRPC_ACK__INVALID ?
0880                   buf.ack.reason : RXRPC_ACK__INVALID);
0881 
0882     trace_rxrpc_rx_ack(call, ack_serial, acked_serial,
0883                first_soft_ack, prev_pkt,
0884                summary.ack_reason, nr_acks);
0885 
0886     switch (buf.ack.reason) {
0887     case RXRPC_ACK_PING_RESPONSE:
0888         rxrpc_input_ping_response(call, skb->tstamp, acked_serial,
0889                       ack_serial);
0890         rxrpc_complete_rtt_probe(call, skb->tstamp, acked_serial, ack_serial,
0891                      rxrpc_rtt_rx_ping_response);
0892         break;
0893     case RXRPC_ACK_REQUESTED:
0894         rxrpc_complete_rtt_probe(call, skb->tstamp, acked_serial, ack_serial,
0895                      rxrpc_rtt_rx_requested_ack);
0896         break;
0897     default:
0898         if (acked_serial != 0)
0899             rxrpc_complete_rtt_probe(call, skb->tstamp, acked_serial, ack_serial,
0900                          rxrpc_rtt_rx_cancel);
0901         break;
0902     }
0903 
0904     if (buf.ack.reason == RXRPC_ACK_PING) {
0905         _proto("Rx ACK %%%u PING Request", ack_serial);
0906         rxrpc_propose_ACK(call, RXRPC_ACK_PING_RESPONSE,
0907                   ack_serial, true, true,
0908                   rxrpc_propose_ack_respond_to_ping);
0909     } else if (sp->hdr.flags & RXRPC_REQUEST_ACK) {
0910         rxrpc_propose_ACK(call, RXRPC_ACK_REQUESTED,
0911                   ack_serial, true, true,
0912                   rxrpc_propose_ack_respond_to_ack);
0913     }
0914 
0915     /* If we get an EXCEEDS_WINDOW ACK from the server, it probably
0916      * indicates that the client address changed due to NAT.  The server
0917      * lost the call because it switched to a different peer.
0918      */
0919     if (unlikely(buf.ack.reason == RXRPC_ACK_EXCEEDS_WINDOW) &&
0920         first_soft_ack == 1 &&
0921         prev_pkt == 0 &&
0922         rxrpc_is_client_call(call)) {
0923         rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
0924                       0, -ENETRESET);
0925         return;
0926     }
0927 
0928     /* If we get an OUT_OF_SEQUENCE ACK from the server, that can also
0929      * indicate a change of address.  However, we can retransmit the call
0930      * if we still have it buffered to the beginning.
0931      */
0932     if (unlikely(buf.ack.reason == RXRPC_ACK_OUT_OF_SEQUENCE) &&
0933         first_soft_ack == 1 &&
0934         prev_pkt == 0 &&
0935         call->tx_hard_ack == 0 &&
0936         rxrpc_is_client_call(call)) {
0937         rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
0938                       0, -ENETRESET);
0939         return;
0940     }
0941 
0942     /* Discard any out-of-order or duplicate ACKs (outside lock). */
0943     if (!rxrpc_is_ack_valid(call, first_soft_ack, prev_pkt)) {
0944         trace_rxrpc_rx_discard_ack(call->debug_id, ack_serial,
0945                        first_soft_ack, call->acks_first_seq,
0946                        prev_pkt, call->acks_prev_seq);
0947         return;
0948     }
0949 
0950     buf.info.rxMTU = 0;
0951     ioffset = offset + nr_acks + 3;
0952     if (skb->len >= ioffset + sizeof(buf.info) &&
0953         skb_copy_bits(skb, ioffset, &buf.info, sizeof(buf.info)) < 0)
0954         return rxrpc_proto_abort("XAI", call, 0);
0955 
0956     spin_lock(&call->input_lock);
0957 
0958     /* Discard any out-of-order or duplicate ACKs (inside lock). */
0959     if (!rxrpc_is_ack_valid(call, first_soft_ack, prev_pkt)) {
0960         trace_rxrpc_rx_discard_ack(call->debug_id, ack_serial,
0961                        first_soft_ack, call->acks_first_seq,
0962                        prev_pkt, call->acks_prev_seq);
0963         goto out;
0964     }
0965     call->acks_latest_ts = skb->tstamp;
0966 
0967     call->acks_first_seq = first_soft_ack;
0968     call->acks_prev_seq = prev_pkt;
0969 
0970     /* Parse rwind and mtu sizes if provided. */
0971     if (buf.info.rxMTU)
0972         rxrpc_input_ackinfo(call, skb, &buf.info);
0973 
0974     if (first_soft_ack == 0) {
0975         rxrpc_proto_abort("AK0", call, 0);
0976         goto out;
0977     }
0978 
0979     /* Ignore ACKs unless we are or have just been transmitting. */
0980     switch (READ_ONCE(call->state)) {
0981     case RXRPC_CALL_CLIENT_SEND_REQUEST:
0982     case RXRPC_CALL_CLIENT_AWAIT_REPLY:
0983     case RXRPC_CALL_SERVER_SEND_REPLY:
0984     case RXRPC_CALL_SERVER_AWAIT_ACK:
0985         break;
0986     default:
0987         goto out;
0988     }
0989 
0990     if (before(hard_ack, call->tx_hard_ack) ||
0991         after(hard_ack, call->tx_top)) {
0992         rxrpc_proto_abort("AKW", call, 0);
0993         goto out;
0994     }
0995     if (nr_acks > call->tx_top - hard_ack) {
0996         rxrpc_proto_abort("AKN", call, 0);
0997         goto out;
0998     }
0999 
1000     if (after(hard_ack, call->tx_hard_ack)) {
1001         if (rxrpc_rotate_tx_window(call, hard_ack, &summary)) {
1002             rxrpc_end_tx_phase(call, false, "ETA");
1003             goto out;
1004         }
1005     }
1006 
1007     if (nr_acks > 0) {
1008         if (skb_copy_bits(skb, offset, buf.acks, nr_acks) < 0) {
1009             rxrpc_proto_abort("XSA", call, 0);
1010             goto out;
1011         }
1012         rxrpc_input_soft_acks(call, buf.acks, first_soft_ack, nr_acks,
1013                       &summary);
1014     }
1015 
1016     if (call->rxtx_annotations[call->tx_top & RXRPC_RXTX_BUFF_MASK] &
1017         RXRPC_TX_ANNO_LAST &&
1018         summary.nr_acks == call->tx_top - hard_ack &&
1019         rxrpc_is_client_call(call))
1020         rxrpc_propose_ACK(call, RXRPC_ACK_PING, ack_serial,
1021                   false, true,
1022                   rxrpc_propose_ack_ping_for_lost_reply);
1023 
1024     rxrpc_congestion_management(call, skb, &summary, acked_serial);
1025 out:
1026     spin_unlock(&call->input_lock);
1027 }
1028 
1029 /*
1030  * Process an ACKALL packet.
1031  */
1032 static void rxrpc_input_ackall(struct rxrpc_call *call, struct sk_buff *skb)
1033 {
1034     struct rxrpc_ack_summary summary = { 0 };
1035     struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
1036 
1037     _proto("Rx ACKALL %%%u", sp->hdr.serial);
1038 
1039     spin_lock(&call->input_lock);
1040 
1041     if (rxrpc_rotate_tx_window(call, call->tx_top, &summary))
1042         rxrpc_end_tx_phase(call, false, "ETL");
1043 
1044     spin_unlock(&call->input_lock);
1045 }
1046 
1047 /*
1048  * Process an ABORT packet directed at a call.
1049  */
1050 static void rxrpc_input_abort(struct rxrpc_call *call, struct sk_buff *skb)
1051 {
1052     struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
1053     __be32 wtmp;
1054     u32 abort_code = RX_CALL_DEAD;
1055 
1056     _enter("");
1057 
1058     if (skb->len >= 4 &&
1059         skb_copy_bits(skb, sizeof(struct rxrpc_wire_header),
1060               &wtmp, sizeof(wtmp)) >= 0)
1061         abort_code = ntohl(wtmp);
1062 
1063     trace_rxrpc_rx_abort(call, sp->hdr.serial, abort_code);
1064 
1065     _proto("Rx ABORT %%%u { %x }", sp->hdr.serial, abort_code);
1066 
1067     rxrpc_set_call_completion(call, RXRPC_CALL_REMOTELY_ABORTED,
1068                   abort_code, -ECONNABORTED);
1069 }
1070 
1071 /*
1072  * Process an incoming call packet.
1073  */
1074 static void rxrpc_input_call_packet(struct rxrpc_call *call,
1075                     struct sk_buff *skb)
1076 {
1077     struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
1078     unsigned long timo;
1079 
1080     _enter("%p,%p", call, skb);
1081 
1082     timo = READ_ONCE(call->next_rx_timo);
1083     if (timo) {
1084         unsigned long now = jiffies, expect_rx_by;
1085 
1086         expect_rx_by = now + timo;
1087         WRITE_ONCE(call->expect_rx_by, expect_rx_by);
1088         rxrpc_reduce_call_timer(call, expect_rx_by, now,
1089                     rxrpc_timer_set_for_normal);
1090     }
1091 
1092     switch (sp->hdr.type) {
1093     case RXRPC_PACKET_TYPE_DATA:
1094         rxrpc_input_data(call, skb);
1095         goto no_free;
1096 
1097     case RXRPC_PACKET_TYPE_ACK:
1098         rxrpc_input_ack(call, skb);
1099         break;
1100 
1101     case RXRPC_PACKET_TYPE_BUSY:
1102         _proto("Rx BUSY %%%u", sp->hdr.serial);
1103 
1104         /* Just ignore BUSY packets from the server; the retry and
1105          * lifespan timers will take care of business.  BUSY packets
1106          * from the client don't make sense.
1107          */
1108         break;
1109 
1110     case RXRPC_PACKET_TYPE_ABORT:
1111         rxrpc_input_abort(call, skb);
1112         break;
1113 
1114     case RXRPC_PACKET_TYPE_ACKALL:
1115         rxrpc_input_ackall(call, skb);
1116         break;
1117 
1118     default:
1119         break;
1120     }
1121 
1122     rxrpc_free_skb(skb, rxrpc_skb_freed);
1123 no_free:
1124     _leave("");
1125 }
1126 
1127 /*
1128  * Handle a new service call on a channel implicitly completing the preceding
1129  * call on that channel.  This does not apply to client conns.
1130  *
1131  * TODO: If callNumber > call_id + 1, renegotiate security.
1132  */
1133 static void rxrpc_input_implicit_end_call(struct rxrpc_sock *rx,
1134                       struct rxrpc_connection *conn,
1135                       struct rxrpc_call *call)
1136 {
1137     switch (READ_ONCE(call->state)) {
1138     case RXRPC_CALL_SERVER_AWAIT_ACK:
1139         rxrpc_call_completed(call);
1140         fallthrough;
1141     case RXRPC_CALL_COMPLETE:
1142         break;
1143     default:
1144         if (rxrpc_abort_call("IMP", call, 0, RX_CALL_DEAD, -ESHUTDOWN)) {
1145             set_bit(RXRPC_CALL_EV_ABORT, &call->events);
1146             rxrpc_queue_call(call);
1147         }
1148         trace_rxrpc_improper_term(call);
1149         break;
1150     }
1151 
1152     spin_lock(&rx->incoming_lock);
1153     __rxrpc_disconnect_call(conn, call);
1154     spin_unlock(&rx->incoming_lock);
1155 }
1156 
1157 /*
1158  * post connection-level events to the connection
1159  * - this includes challenges, responses, some aborts and call terminal packet
1160  *   retransmission.
1161  */
1162 static void rxrpc_post_packet_to_conn(struct rxrpc_connection *conn,
1163                       struct sk_buff *skb)
1164 {
1165     _enter("%p,%p", conn, skb);
1166 
1167     skb_queue_tail(&conn->rx_queue, skb);
1168     rxrpc_queue_conn(conn);
1169 }
1170 
1171 /*
1172  * post endpoint-level events to the local endpoint
1173  * - this includes debug and version messages
1174  */
1175 static void rxrpc_post_packet_to_local(struct rxrpc_local *local,
1176                        struct sk_buff *skb)
1177 {
1178     _enter("%p,%p", local, skb);
1179 
1180     if (rxrpc_get_local_maybe(local)) {
1181         skb_queue_tail(&local->event_queue, skb);
1182         rxrpc_queue_local(local);
1183     } else {
1184         rxrpc_free_skb(skb, rxrpc_skb_freed);
1185     }
1186 }
1187 
1188 /*
1189  * put a packet up for transport-level abort
1190  */
1191 static void rxrpc_reject_packet(struct rxrpc_local *local, struct sk_buff *skb)
1192 {
1193     if (rxrpc_get_local_maybe(local)) {
1194         skb_queue_tail(&local->reject_queue, skb);
1195         rxrpc_queue_local(local);
1196     } else {
1197         rxrpc_free_skb(skb, rxrpc_skb_freed);
1198     }
1199 }
1200 
1201 /*
1202  * Extract the wire header from a packet and translate the byte order.
1203  */
1204 static noinline
1205 int rxrpc_extract_header(struct rxrpc_skb_priv *sp, struct sk_buff *skb)
1206 {
1207     struct rxrpc_wire_header whdr;
1208 
1209     /* dig out the RxRPC connection details */
1210     if (skb_copy_bits(skb, 0, &whdr, sizeof(whdr)) < 0) {
1211         trace_rxrpc_rx_eproto(NULL, sp->hdr.serial,
1212                       tracepoint_string("bad_hdr"));
1213         return -EBADMSG;
1214     }
1215 
1216     memset(sp, 0, sizeof(*sp));
1217     sp->hdr.epoch       = ntohl(whdr.epoch);
1218     sp->hdr.cid     = ntohl(whdr.cid);
1219     sp->hdr.callNumber  = ntohl(whdr.callNumber);
1220     sp->hdr.seq     = ntohl(whdr.seq);
1221     sp->hdr.serial      = ntohl(whdr.serial);
1222     sp->hdr.flags       = whdr.flags;
1223     sp->hdr.type        = whdr.type;
1224     sp->hdr.userStatus  = whdr.userStatus;
1225     sp->hdr.securityIndex   = whdr.securityIndex;
1226     sp->hdr._rsvd       = ntohs(whdr._rsvd);
1227     sp->hdr.serviceId   = ntohs(whdr.serviceId);
1228     return 0;
1229 }
1230 
1231 /*
1232  * handle data received on the local endpoint
1233  * - may be called in interrupt context
1234  *
1235  * [!] Note that as this is called from the encap_rcv hook, the socket is not
1236  * held locked by the caller and nothing prevents sk_user_data on the UDP from
1237  * being cleared in the middle of processing this function.
1238  *
1239  * Called with the RCU read lock held from the IP layer via UDP.
1240  */
1241 int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb)
1242 {
1243     struct rxrpc_local *local = rcu_dereference_sk_user_data(udp_sk);
1244     struct rxrpc_connection *conn;
1245     struct rxrpc_channel *chan;
1246     struct rxrpc_call *call = NULL;
1247     struct rxrpc_skb_priv *sp;
1248     struct rxrpc_peer *peer = NULL;
1249     struct rxrpc_sock *rx = NULL;
1250     unsigned int channel;
1251 
1252     _enter("%p", udp_sk);
1253 
1254     if (unlikely(!local)) {
1255         kfree_skb(skb);
1256         return 0;
1257     }
1258     if (skb->tstamp == 0)
1259         skb->tstamp = ktime_get_real();
1260 
1261     rxrpc_new_skb(skb, rxrpc_skb_received);
1262 
1263     skb_pull(skb, sizeof(struct udphdr));
1264 
1265     /* The UDP protocol already released all skb resources;
1266      * we are free to add our own data there.
1267      */
1268     sp = rxrpc_skb(skb);
1269 
1270     /* dig out the RxRPC connection details */
1271     if (rxrpc_extract_header(sp, skb) < 0)
1272         goto bad_message;
1273 
1274     if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
1275         static int lose;
1276         if ((lose++ & 7) == 7) {
1277             trace_rxrpc_rx_lose(sp);
1278             rxrpc_free_skb(skb, rxrpc_skb_lost);
1279             return 0;
1280         }
1281     }
1282 
1283     if (skb->tstamp == 0)
1284         skb->tstamp = ktime_get_real();
1285     trace_rxrpc_rx_packet(sp);
1286 
1287     switch (sp->hdr.type) {
1288     case RXRPC_PACKET_TYPE_VERSION:
1289         if (rxrpc_to_client(sp))
1290             goto discard;
1291         rxrpc_post_packet_to_local(local, skb);
1292         goto out;
1293 
1294     case RXRPC_PACKET_TYPE_BUSY:
1295         if (rxrpc_to_server(sp))
1296             goto discard;
1297         fallthrough;
1298     case RXRPC_PACKET_TYPE_ACK:
1299     case RXRPC_PACKET_TYPE_ACKALL:
1300         if (sp->hdr.callNumber == 0)
1301             goto bad_message;
1302         fallthrough;
1303     case RXRPC_PACKET_TYPE_ABORT:
1304         break;
1305 
1306     case RXRPC_PACKET_TYPE_DATA:
1307         if (sp->hdr.callNumber == 0 ||
1308             sp->hdr.seq == 0)
1309             goto bad_message;
1310         if (!rxrpc_validate_data(skb))
1311             goto bad_message;
1312 
1313         /* Unshare the packet so that it can be modified for in-place
1314          * decryption.
1315          */
1316         if (sp->hdr.securityIndex != 0) {
1317             struct sk_buff *nskb = skb_unshare(skb, GFP_ATOMIC);
1318             if (!nskb) {
1319                 rxrpc_eaten_skb(skb, rxrpc_skb_unshared_nomem);
1320                 goto out;
1321             }
1322 
1323             if (nskb != skb) {
1324                 rxrpc_eaten_skb(skb, rxrpc_skb_received);
1325                 skb = nskb;
1326                 rxrpc_new_skb(skb, rxrpc_skb_unshared);
1327                 sp = rxrpc_skb(skb);
1328             }
1329         }
1330         break;
1331 
1332     case RXRPC_PACKET_TYPE_CHALLENGE:
1333         if (rxrpc_to_server(sp))
1334             goto discard;
1335         break;
1336     case RXRPC_PACKET_TYPE_RESPONSE:
1337         if (rxrpc_to_client(sp))
1338             goto discard;
1339         break;
1340 
1341         /* Packet types 9-11 should just be ignored. */
1342     case RXRPC_PACKET_TYPE_PARAMS:
1343     case RXRPC_PACKET_TYPE_10:
1344     case RXRPC_PACKET_TYPE_11:
1345         goto discard;
1346 
1347     default:
1348         _proto("Rx Bad Packet Type %u", sp->hdr.type);
1349         goto bad_message;
1350     }
1351 
1352     if (sp->hdr.serviceId == 0)
1353         goto bad_message;
1354 
1355     if (rxrpc_to_server(sp)) {
1356         /* Weed out packets to services we're not offering.  Packets
1357          * that would begin a call are explicitly rejected and the rest
1358          * are just discarded.
1359          */
1360         rx = rcu_dereference(local->service);
1361         if (!rx || (sp->hdr.serviceId != rx->srx.srx_service &&
1362                 sp->hdr.serviceId != rx->second_service)) {
1363             if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA &&
1364                 sp->hdr.seq == 1)
1365                 goto unsupported_service;
1366             goto discard;
1367         }
1368     }
1369 
1370     conn = rxrpc_find_connection_rcu(local, skb, &peer);
1371     if (conn) {
1372         if (sp->hdr.securityIndex != conn->security_ix)
1373             goto wrong_security;
1374 
1375         if (sp->hdr.serviceId != conn->service_id) {
1376             int old_id;
1377 
1378             if (!test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags))
1379                 goto reupgrade;
1380             old_id = cmpxchg(&conn->service_id, conn->params.service_id,
1381                      sp->hdr.serviceId);
1382 
1383             if (old_id != conn->params.service_id &&
1384                 old_id != sp->hdr.serviceId)
1385                 goto reupgrade;
1386         }
1387 
1388         if (sp->hdr.callNumber == 0) {
1389             /* Connection-level packet */
1390             _debug("CONN %p {%d}", conn, conn->debug_id);
1391             rxrpc_post_packet_to_conn(conn, skb);
1392             goto out;
1393         }
1394 
1395         if ((int)sp->hdr.serial - (int)conn->hi_serial > 0)
1396             conn->hi_serial = sp->hdr.serial;
1397 
1398         /* Call-bound packets are routed by connection channel. */
1399         channel = sp->hdr.cid & RXRPC_CHANNELMASK;
1400         chan = &conn->channels[channel];
1401 
1402         /* Ignore really old calls */
1403         if (sp->hdr.callNumber < chan->last_call)
1404             goto discard;
1405 
1406         if (sp->hdr.callNumber == chan->last_call) {
1407             if (chan->call ||
1408                 sp->hdr.type == RXRPC_PACKET_TYPE_ABORT)
1409                 goto discard;
1410 
1411             /* For the previous service call, if completed
1412              * successfully, we discard all further packets.
1413              */
1414             if (rxrpc_conn_is_service(conn) &&
1415                 chan->last_type == RXRPC_PACKET_TYPE_ACK)
1416                 goto discard;
1417 
1418             /* But otherwise we need to retransmit the final packet
1419              * from data cached in the connection record.
1420              */
1421             if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA)
1422                 trace_rxrpc_rx_data(chan->call_debug_id,
1423                             sp->hdr.seq,
1424                             sp->hdr.serial,
1425                             sp->hdr.flags, 0);
1426             rxrpc_post_packet_to_conn(conn, skb);
1427             goto out;
1428         }
1429 
1430         call = rcu_dereference(chan->call);
1431 
1432         if (sp->hdr.callNumber > chan->call_id) {
1433             if (rxrpc_to_client(sp))
1434                 goto reject_packet;
1435             if (call)
1436                 rxrpc_input_implicit_end_call(rx, conn, call);
1437             call = NULL;
1438         }
1439 
1440         if (call) {
1441             if (sp->hdr.serviceId != call->service_id)
1442                 call->service_id = sp->hdr.serviceId;
1443             if ((int)sp->hdr.serial - (int)call->rx_serial > 0)
1444                 call->rx_serial = sp->hdr.serial;
1445             if (!test_bit(RXRPC_CALL_RX_HEARD, &call->flags))
1446                 set_bit(RXRPC_CALL_RX_HEARD, &call->flags);
1447         }
1448     }
1449 
1450     if (!call || refcount_read(&call->ref) == 0) {
1451         if (rxrpc_to_client(sp) ||
1452             sp->hdr.type != RXRPC_PACKET_TYPE_DATA)
1453             goto bad_message;
1454         if (sp->hdr.seq != 1)
1455             goto discard;
1456         call = rxrpc_new_incoming_call(local, rx, skb);
1457         if (!call)
1458             goto reject_packet;
1459     }
1460 
1461     /* Process a call packet; this either discards or passes on the ref
1462      * elsewhere.
1463      */
1464     rxrpc_input_call_packet(call, skb);
1465     goto out;
1466 
1467 discard:
1468     rxrpc_free_skb(skb, rxrpc_skb_freed);
1469 out:
1470     trace_rxrpc_rx_done(0, 0);
1471     return 0;
1472 
1473 wrong_security:
1474     trace_rxrpc_abort(0, "SEC", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
1475               RXKADINCONSISTENCY, EBADMSG);
1476     skb->priority = RXKADINCONSISTENCY;
1477     goto post_abort;
1478 
1479 unsupported_service:
1480     trace_rxrpc_abort(0, "INV", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
1481               RX_INVALID_OPERATION, EOPNOTSUPP);
1482     skb->priority = RX_INVALID_OPERATION;
1483     goto post_abort;
1484 
1485 reupgrade:
1486     trace_rxrpc_abort(0, "UPG", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
1487               RX_PROTOCOL_ERROR, EBADMSG);
1488     goto protocol_error;
1489 
1490 bad_message:
1491     trace_rxrpc_abort(0, "BAD", sp->hdr.cid, sp->hdr.callNumber, sp->hdr.seq,
1492               RX_PROTOCOL_ERROR, EBADMSG);
1493 protocol_error:
1494     skb->priority = RX_PROTOCOL_ERROR;
1495 post_abort:
1496     skb->mark = RXRPC_SKB_MARK_REJECT_ABORT;
1497 reject_packet:
1498     trace_rxrpc_rx_done(skb->mark, skb->priority);
1499     rxrpc_reject_packet(local, skb);
1500     _leave(" [badmsg]");
1501     return 0;
1502 }
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