net/bridge/br_stp_bpdu.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *  Spanning tree protocol; BPDU handling
0004  *  Linux ethernet bridge
0005  *
0006  *  Authors:
0007  *  Lennert Buytenhek       <buytenh@gnu.org>
0008  */
0009
0010 #include <linux/kernel.h>
0011 #include <linux/netfilter_bridge.h>
0012 #include <linux/etherdevice.h>
0013 #include <linux/llc.h>
0014 #include <linux/slab.h>
0015 #include <linux/pkt_sched.h>
0016 #include <net/net_namespace.h>
0017 #include <net/llc.h>
0018 #include <net/llc_pdu.h>
0019 #include <net/stp.h>
0020 #include <asm/unaligned.h>
0021
0022 #include "br_private.h"
0023 #include "br_private_stp.h"
0024
0025 #define STP_HZ      256
0026
0027 #define LLC_RESERVE sizeof(struct llc_pdu_un)
0028
0029 static int br_send_bpdu_finish(struct net *net, struct sock *sk,
0030                    struct sk_buff *skb)
0031 {
0032     return dev_queue_xmit(skb);
0033 }
0034
0035 static void br_send_bpdu(struct net_bridge_port *p,
0036              const unsigned char *data, int length)
0037 {
0038     struct sk_buff *skb;
0039
0040     skb = dev_alloc_skb(length+LLC_RESERVE);
0041     if (!skb)
0042         return;
0043
0044     skb->dev = p->dev;
0045     skb->protocol = htons(ETH_P_802_2);
0046     skb->priority = TC_PRIO_CONTROL;
0047
0048     skb_reserve(skb, LLC_RESERVE);
0049     __skb_put_data(skb, data, length);
0050
0051     llc_pdu_header_init(skb, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
0052                 LLC_SAP_BSPAN, LLC_PDU_CMD);
0053     llc_pdu_init_as_ui_cmd(skb);
0054
0055     llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr);
0056
0057     skb_reset_mac_header(skb);
0058
0059     NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT,
0060         dev_net(p->dev), NULL, skb, NULL, skb->dev,
0061         br_send_bpdu_finish);
0062 }
0063
0064 static inline void br_set_ticks(unsigned char *dest, int j)
0065 {
0066     unsigned long ticks = (STP_HZ * j)/ HZ;
0067
0068     put_unaligned_be16(ticks, dest);
0069 }
0070
0071 static inline int br_get_ticks(const unsigned char *src)
0072 {
0073     unsigned long ticks = get_unaligned_be16(src);
0074
0075     return DIV_ROUND_UP(ticks * HZ, STP_HZ);
0076 }
0077
0078 /* called under bridge lock */
0079 void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
0080 {
0081     unsigned char buf[35];
0082
0083     if (p->br->stp_enabled != BR_KERNEL_STP)
0084         return;
0085
0086     buf[0] = 0;
0087     buf[1] = 0;
0088     buf[2] = 0;
0089     buf[3] = BPDU_TYPE_CONFIG;
0090     buf[4] = (bpdu->topology_change ? 0x01 : 0) |
0091         (bpdu->topology_change_ack ? 0x80 : 0);
0092     buf[5] = bpdu->root.prio[0];
0093     buf[6] = bpdu->root.prio[1];
0094     buf[7] = bpdu->root.addr[0];
0095     buf[8] = bpdu->root.addr[1];
0096     buf[9] = bpdu->root.addr[2];
0097     buf[10] = bpdu->root.addr[3];
0098     buf[11] = bpdu->root.addr[4];
0099     buf[12] = bpdu->root.addr[5];
0100     buf[13] = (bpdu->root_path_cost >> 24) & 0xFF;
0101     buf[14] = (bpdu->root_path_cost >> 16) & 0xFF;
0102     buf[15] = (bpdu->root_path_cost >> 8) & 0xFF;
0103     buf[16] = bpdu->root_path_cost & 0xFF;
0104     buf[17] = bpdu->bridge_id.prio[0];
0105     buf[18] = bpdu->bridge_id.prio[1];
0106     buf[19] = bpdu->bridge_id.addr[0];
0107     buf[20] = bpdu->bridge_id.addr[1];
0108     buf[21] = bpdu->bridge_id.addr[2];
0109     buf[22] = bpdu->bridge_id.addr[3];
0110     buf[23] = bpdu->bridge_id.addr[4];
0111     buf[24] = bpdu->bridge_id.addr[5];
0112     buf[25] = (bpdu->port_id >> 8) & 0xFF;
0113     buf[26] = bpdu->port_id & 0xFF;
0114
0115     br_set_ticks(buf+27, bpdu->message_age);
0116     br_set_ticks(buf+29, bpdu->max_age);
0117     br_set_ticks(buf+31, bpdu->hello_time);
0118     br_set_ticks(buf+33, bpdu->forward_delay);
0119
0120     br_send_bpdu(p, buf, 35);
0121
0122     p->stp_xstats.tx_bpdu++;
0123 }
0124
0125 /* called under bridge lock */
0126 void br_send_tcn_bpdu(struct net_bridge_port *p)
0127 {
0128     unsigned char buf[4];
0129
0130     if (p->br->stp_enabled != BR_KERNEL_STP)
0131         return;
0132
0133     buf[0] = 0;
0134     buf[1] = 0;
0135     buf[2] = 0;
0136     buf[3] = BPDU_TYPE_TCN;
0137     br_send_bpdu(p, buf, 4);
0138
0139     p->stp_xstats.tx_tcn++;
0140 }
0141
0142 /*
0143  * Called from llc.
0144  *
0145  * NO locks, but rcu_read_lock
0146  */
0147 void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
0148         struct net_device *dev)
0149 {
0150     struct net_bridge_port *p;
0151     struct net_bridge *br;
0152     const unsigned char *buf;
0153
0154     if (!pskb_may_pull(skb, 4))
0155         goto err;
0156
0157     /* compare of protocol id and version */
0158     buf = skb->data;
0159     if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
0160         goto err;
0161
0162     p = br_port_get_check_rcu(dev);
0163     if (!p)
0164         goto err;
0165
0166     br = p->br;
0167     spin_lock(&br->lock);
0168
0169     if (br->stp_enabled != BR_KERNEL_STP)
0170         goto out;
0171
0172     if (!(br->dev->flags & IFF_UP))
0173         goto out;
0174
0175     if (p->state == BR_STATE_DISABLED)
0176         goto out;
0177
0178     if (!ether_addr_equal(eth_hdr(skb)->h_dest, br->group_addr))
0179         goto out;
0180
0181     if (p->flags & BR_BPDU_GUARD) {
0182         br_notice(br, "BPDU received on blocked port %u(%s)\n",
0183               (unsigned int) p->port_no, p->dev->name);
0184         br_stp_disable_port(p);
0185         goto out;
0186     }
0187
0188     buf = skb_pull(skb, 3);
0189
0190     if (buf[0] == BPDU_TYPE_CONFIG) {
0191         struct br_config_bpdu bpdu;
0192
0193         if (!pskb_may_pull(skb, 32))
0194             goto out;
0195
0196         buf = skb->data;
0197         bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
0198         bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
0199
0200         bpdu.root.prio[0] = buf[2];
0201         bpdu.root.prio[1] = buf[3];
0202         bpdu.root.addr[0] = buf[4];
0203         bpdu.root.addr[1] = buf[5];
0204         bpdu.root.addr[2] = buf[6];
0205         bpdu.root.addr[3] = buf[7];
0206         bpdu.root.addr[4] = buf[8];
0207         bpdu.root.addr[5] = buf[9];
0208         bpdu.root_path_cost =
0209             (buf[10] << 24) |
0210             (buf[11] << 16) |
0211             (buf[12] << 8) |
0212             buf[13];
0213         bpdu.bridge_id.prio[0] = buf[14];
0214         bpdu.bridge_id.prio[1] = buf[15];
0215         bpdu.bridge_id.addr[0] = buf[16];
0216         bpdu.bridge_id.addr[1] = buf[17];
0217         bpdu.bridge_id.addr[2] = buf[18];
0218         bpdu.bridge_id.addr[3] = buf[19];
0219         bpdu.bridge_id.addr[4] = buf[20];
0220         bpdu.bridge_id.addr[5] = buf[21];
0221         bpdu.port_id = (buf[22] << 8) | buf[23];
0222
0223         bpdu.message_age = br_get_ticks(buf+24);
0224         bpdu.max_age = br_get_ticks(buf+26);
0225         bpdu.hello_time = br_get_ticks(buf+28);
0226         bpdu.forward_delay = br_get_ticks(buf+30);
0227
0228         if (bpdu.message_age > bpdu.max_age) {
0229             if (net_ratelimit())
0230                 br_notice(p->br,
0231                       "port %u config from %pM"
0232                       " (message_age %ul > max_age %ul)\n",
0233                       p->port_no,
0234                       eth_hdr(skb)->h_source,
0235                       bpdu.message_age, bpdu.max_age);
0236             goto out;
0237         }
0238
0239         br_received_config_bpdu(p, &bpdu);
0240     } else if (buf[0] == BPDU_TYPE_TCN) {
0241         br_received_tcn_bpdu(p);
0242     }
0243  out:
0244     spin_unlock(&br->lock);
0245  err:
0246     kfree_skb(skb);
0247 }