net/netrom/nr_out.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *
0004  * Copyright Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
0005  * Copyright Darryl Miles G7LED (dlm@g7led.demon.co.uk)
0006  */
0007 #include <linux/errno.h>
0008 #include <linux/types.h>
0009 #include <linux/socket.h>
0010 #include <linux/in.h>
0011 #include <linux/kernel.h>
0012 #include <linux/timer.h>
0013 #include <linux/string.h>
0014 #include <linux/sockios.h>
0015 #include <linux/net.h>
0016 #include <linux/slab.h>
0017 #include <net/ax25.h>
0018 #include <linux/inet.h>
0019 #include <linux/netdevice.h>
0020 #include <linux/skbuff.h>
0021 #include <net/sock.h>
0022 #include <linux/uaccess.h>
0023 #include <linux/fcntl.h>
0024 #include <linux/mm.h>
0025 #include <linux/interrupt.h>
0026 #include <net/netrom.h>
0027
0028 /*
0029  *  This is where all NET/ROM frames pass, except for IP-over-NET/ROM which
0030  *  cannot be fragmented in this manner.
0031  */
0032 void nr_output(struct sock *sk, struct sk_buff *skb)
0033 {
0034     struct sk_buff *skbn;
0035     unsigned char transport[NR_TRANSPORT_LEN];
0036     int err, frontlen, len;
0037
0038     if (skb->len - NR_TRANSPORT_LEN > NR_MAX_PACKET_SIZE) {
0039         /* Save a copy of the Transport Header */
0040         skb_copy_from_linear_data(skb, transport, NR_TRANSPORT_LEN);
0041         skb_pull(skb, NR_TRANSPORT_LEN);
0042
0043         frontlen = skb_headroom(skb);
0044
0045         while (skb->len > 0) {
0046             if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
0047                 return;
0048
0049             skb_reserve(skbn, frontlen);
0050
0051             len = (NR_MAX_PACKET_SIZE > skb->len) ? skb->len : NR_MAX_PACKET_SIZE;
0052
0053             /* Copy the user data */
0054             skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
0055             skb_pull(skb, len);
0056
0057             /* Duplicate the Transport Header */
0058             skb_push(skbn, NR_TRANSPORT_LEN);
0059             skb_copy_to_linear_data(skbn, transport,
0060                         NR_TRANSPORT_LEN);
0061             if (skb->len > 0)
0062                 skbn->data[4] |= NR_MORE_FLAG;
0063
0064             skb_queue_tail(&sk->sk_write_queue, skbn); /* Throw it on the queue */
0065         }
0066
0067         kfree_skb(skb);
0068     } else {
0069         skb_queue_tail(&sk->sk_write_queue, skb);       /* Throw it on the queue */
0070     }
0071
0072     nr_kick(sk);
0073 }
0074
0075 /*
0076  *  This procedure is passed a buffer descriptor for an iframe. It builds
0077  *  the rest of the control part of the frame and then writes it out.
0078  */
0079 static void nr_send_iframe(struct sock *sk, struct sk_buff *skb)
0080 {
0081     struct nr_sock *nr = nr_sk(sk);
0082
0083     if (skb == NULL)
0084         return;
0085
0086     skb->data[2] = nr->vs;
0087     skb->data[3] = nr->vr;
0088
0089     if (nr->condition & NR_COND_OWN_RX_BUSY)
0090         skb->data[4] |= NR_CHOKE_FLAG;
0091
0092     nr_start_idletimer(sk);
0093
0094     nr_transmit_buffer(sk, skb);
0095 }
0096
0097 void nr_send_nak_frame(struct sock *sk)
0098 {
0099     struct sk_buff *skb, *skbn;
0100     struct nr_sock *nr = nr_sk(sk);
0101
0102     if ((skb = skb_peek(&nr->ack_queue)) == NULL)
0103         return;
0104
0105     if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL)
0106         return;
0107
0108     skbn->data[2] = nr->va;
0109     skbn->data[3] = nr->vr;
0110
0111     if (nr->condition & NR_COND_OWN_RX_BUSY)
0112         skbn->data[4] |= NR_CHOKE_FLAG;
0113
0114     nr_transmit_buffer(sk, skbn);
0115
0116     nr->condition &= ~NR_COND_ACK_PENDING;
0117     nr->vl         = nr->vr;
0118
0119     nr_stop_t1timer(sk);
0120 }
0121
0122 void nr_kick(struct sock *sk)
0123 {
0124     struct nr_sock *nr = nr_sk(sk);
0125     struct sk_buff *skb, *skbn;
0126     unsigned short start, end;
0127
0128     if (nr->state != NR_STATE_3)
0129         return;
0130
0131     if (nr->condition & NR_COND_PEER_RX_BUSY)
0132         return;
0133
0134     if (!skb_peek(&sk->sk_write_queue))
0135         return;
0136
0137     start = (skb_peek(&nr->ack_queue) == NULL) ? nr->va : nr->vs;
0138     end   = (nr->va + nr->window) % NR_MODULUS;
0139
0140     if (start == end)
0141         return;
0142
0143     nr->vs = start;
0144
0145     /*
0146      * Transmit data until either we're out of data to send or
0147      * the window is full.
0148      */
0149
0150     /*
0151      * Dequeue the frame and copy it.
0152      */
0153     skb = skb_dequeue(&sk->sk_write_queue);
0154
0155     do {
0156         if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
0157             skb_queue_head(&sk->sk_write_queue, skb);
0158             break;
0159         }
0160
0161         skb_set_owner_w(skbn, sk);
0162
0163         /*
0164          * Transmit the frame copy.
0165          */
0166         nr_send_iframe(sk, skbn);
0167
0168         nr->vs = (nr->vs + 1) % NR_MODULUS;
0169
0170         /*
0171          * Requeue the original data frame.
0172          */
0173         skb_queue_tail(&nr->ack_queue, skb);
0174
0175     } while (nr->vs != end &&
0176          (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
0177
0178     nr->vl         = nr->vr;
0179     nr->condition &= ~NR_COND_ACK_PENDING;
0180
0181     if (!nr_t1timer_running(sk))
0182         nr_start_t1timer(sk);
0183 }
0184
0185 void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
0186 {
0187     struct nr_sock *nr = nr_sk(sk);
0188     unsigned char *dptr;
0189
0190     /*
0191      *  Add the protocol byte and network header.
0192      */
0193     dptr = skb_push(skb, NR_NETWORK_LEN);
0194
0195     memcpy(dptr, &nr->source_addr, AX25_ADDR_LEN);
0196     dptr[6] &= ~AX25_CBIT;
0197     dptr[6] &= ~AX25_EBIT;
0198     dptr[6] |= AX25_SSSID_SPARE;
0199     dptr += AX25_ADDR_LEN;
0200
0201     memcpy(dptr, &nr->dest_addr, AX25_ADDR_LEN);
0202     dptr[6] &= ~AX25_CBIT;
0203     dptr[6] |= AX25_EBIT;
0204     dptr[6] |= AX25_SSSID_SPARE;
0205     dptr += AX25_ADDR_LEN;
0206
0207     *dptr++ = sysctl_netrom_network_ttl_initialiser;
0208
0209     if (!nr_route_frame(skb, NULL)) {
0210         kfree_skb(skb);
0211         nr_disconnect(sk, ENETUNREACH);
0212     }
0213 }
0214
0215 /*
0216  * The following routines are taken from page 170 of the 7th ARRL Computer
0217  * Networking Conference paper, as is the whole state machine.
0218  */
0219
0220 void nr_establish_data_link(struct sock *sk)
0221 {
0222     struct nr_sock *nr = nr_sk(sk);
0223
0224     nr->condition = 0x00;
0225     nr->n2count   = 0;
0226
0227     nr_write_internal(sk, NR_CONNREQ);
0228
0229     nr_stop_t2timer(sk);
0230     nr_stop_t4timer(sk);
0231     nr_stop_idletimer(sk);
0232     nr_start_t1timer(sk);
0233 }
0234
0235 /*
0236  * Never send a NAK when we are CHOKEd.
0237  */
0238 void nr_enquiry_response(struct sock *sk)
0239 {
0240     struct nr_sock *nr = nr_sk(sk);
0241     int frametype = NR_INFOACK;
0242
0243     if (nr->condition & NR_COND_OWN_RX_BUSY) {
0244         frametype |= NR_CHOKE_FLAG;
0245     } else {
0246         if (skb_peek(&nr->reseq_queue) != NULL)
0247             frametype |= NR_NAK_FLAG;
0248     }
0249
0250     nr_write_internal(sk, frametype);
0251
0252     nr->vl         = nr->vr;
0253     nr->condition &= ~NR_COND_ACK_PENDING;
0254 }
0255
0256 void nr_check_iframes_acked(struct sock *sk, unsigned short nr)
0257 {
0258     struct nr_sock *nrom = nr_sk(sk);
0259
0260     if (nrom->vs == nr) {
0261         nr_frames_acked(sk, nr);
0262         nr_stop_t1timer(sk);
0263         nrom->n2count = 0;
0264     } else {
0265         if (nrom->va != nr) {
0266             nr_frames_acked(sk, nr);
0267             nr_start_t1timer(sk);
0268         }
0269     }
0270 }