packet.c

   1 /*****************************************************************************
   2   Copyright (c) 2006 EMC Corporation.
   3
   4   This program is free software; you can redistribute it and/or modify it
   5   under the terms of the GNU General Public License as published by the Free
   6   Software Foundation; either version 2 of the License, or (at your option)
   7   any later version.
   8
   9   This program is distributed in the hope that it will be useful, but WITHOUT
  10   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12   more details.
  13
  14   You should have received a copy of the GNU General Public License along with
  15   this program; if not, write to the Free Software Foundation, Inc., 59
  16   Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  17
  18   The full GNU General Public License is included in this distribution in the
  19   file called LICENSE.
  20
  21   Authors: Srinivas Aji <Aji_Srinivas@emc.com>
  22            Stephen Hemminger <shemminger@linux-foundation.org>
  23
  24 ******************************************************************************/
  25
  26 #include "packet.h"
  27 #include "epoll_loop.h"
  28 #include "netif_utils.h"
  29 #include "bridge_ctl.h"
  30
  31 #include <stdio.h>
  32 #include <stdlib.h>
  33 #include <errno.h>
  34 #include <string.h>
  35 #include <unistd.h>
  36 #include <stdint.h>
  37 #include <sys/socket.h>
  38 #include <sys/ioctl.h>
  39 #include <fcntl.h>
  40 #include <netinet/in.h>
  41
  42 #include <linux/if.h>
  43 #include <linux/if_ether.h>
  44 #include <linux/if_packet.h>
  45 #include <linux/filter.h>
  46
  47 #include "log.h"
  48
  49 static struct epoll_event_handler packet_event;
  50
  51 #ifdef PACKET_DEBUG
  52 static void dump_packet(const unsigned char *buf, int cc)
  53 {
  54         int i, j;
  55         for (i = 0; i < cc; i += 16) {
  56                 for (j = 0; j < 16 && i + j < cc; j++)
  57                         printf(" %02x", buf[i + j]);
  58                 printf("\n");
  59         }
  60         printf("\n");
  61         fflush(stdout);
  62 }
  63 #endif
  64
  65 /*
  66  * To send/receive Spanning Tree packets we use PF_PACKET because
  67  * it allows the filtering we want but gives raw data
  68  */
  69 void packet_send(int ifindex, const unsigned char *data, int len)
  70 {
  71         int l;
  72         struct sockaddr_ll sl = {
  73                 .sll_family = AF_PACKET,
  74                 .sll_protocol = htons(ETH_P_802_2),
  75                 .sll_ifindex = ifindex,
  76                 .sll_halen = ETH_ALEN,
  77         };
  78
  79         memcpy(&sl.sll_addr, data, ETH_ALEN);
  80
  81 #ifdef PACKET_DEBUG
  82         printf("Transmit Dst index %d %02x:%02x:%02x:%02x:%02x:%02x\n",
  83                sl.sll_ifindex,
  84                sl.sll_addr[0], sl.sll_addr[1], sl.sll_addr[2],
  85                sl.sll_addr[3], sl.sll_addr[4], sl.sll_addr[5]);
  86
  87         dump_packet(data, len);
  88 #endif
  89
  90         l = sendto(packet_event.fd, data, len, 0,
  91                    (struct sockaddr *) &sl, sizeof(sl));
  92
  93         if (l < 0) {
  94                 if (errno != EWOULDBLOCK)
  95                         ERROR("send failed: %m");
  96         } else if (l != len)
  97                 ERROR("short write in sendto: %d instead of %d", l, len);
  98 }
  99
 100 static void packet_rcv(uint32_t events, struct epoll_event_handler *h)
 101 {
 102         int cc;
 103         unsigned char buf[2048];
 104         struct sockaddr_ll sl;
 105         socklen_t salen = sizeof sl;
 106
 107         cc = recvfrom(h->fd, &buf, sizeof(buf), 0, (struct sockaddr *) &sl, &salen);
 108         if (cc <= 0) {
 109                 ERROR("recvfrom failed: %m");
 110                 return;
 111         }
 112
 113 #ifdef PACKET_DEBUG
 114         printf("Receive Src ifindex %d %02x:%02x:%02x:%02x:%02x:%02x\n",
 115                sl.sll_ifindex,
 116                sl.sll_addr[0], sl.sll_addr[1], sl.sll_addr[2],
 117                sl.sll_addr[3], sl.sll_addr[4], sl.sll_addr[5]);
 118
 119         dump_packet(buf, cc);
 120 #endif
 121
 122         bridge_bpdu_rcv(sl.sll_ifindex, buf, cc);
 123 }
 124
 125 /* Berkeley Packet filter code to filter out spanning tree packets.
 126    from tcpdump -dd stp
 127  */
 128 static struct sock_filter stp_filter[] = {
 129         { 0x28, 0, 0, 0x0000000c },
 130         { 0x25, 3, 0, 0x000005dc },
 131         { 0x30, 0, 0, 0x0000000e },
 132         { 0x15, 0, 1, 0x00000042 },
 133         { 0x6, 0, 0, 0x00000060 },
 134         { 0x6, 0, 0, 0x00000000 },
 135 };
 136
 137 /*
 138  * Open up a raw packet socket to catch all 802.2 packets.
 139  * and install a packet filter to only see STP (SAP 42)
 140  *
 141  * Since any bridged devices are already in promiscious mode
 142  * no need to add multicast address.
 143  */
 144 int packet_sock_init(void)
 145 {
 146         int s;
 147         struct sock_fprog prog = {
 148                 .len = sizeof(stp_filter) / sizeof(stp_filter[0]),
 149                 .filter = stp_filter,
 150         };
 151
 152         s = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_802_2));
 153         if (s < 0) {
 154                 ERROR("socket failed: %m");
 155                 return -1;
 156         }
 157
 158         if (setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &prog, sizeof(prog)) < 0)
 159                 ERROR("setsockopt packet filter failed: %m");
 160
 161         else if (fcntl(s, F_SETFL, O_NONBLOCK) < 0)
 162                 ERROR("fcntl set nonblock failed: %m");
 163
 164         else {
 165                 packet_event.fd = s;
 166                 packet_event.handler = packet_rcv;
 167
 168                 if (add_epoll(&packet_event) == 0)
 169                         return 0;
 170         }
 171
 172         close(s);
 173         return -1;
 174 }