lib/packets.c

   1 /*
   2  * Copyright (c) 2009, 2010, 2011 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "packets.h"
  19 #include <assert.h>
  20 #include <arpa/inet.h>
  21 #include <netinet/in.h>
  22 #include <stdlib.h>
  23 #include "byte-order.h"
  24 #include "dynamic-string.h"
  25 #include "ofpbuf.h"
  26
  27 const struct in6_addr in6addr_exact = IN6ADDR_EXACT_INIT;
  28
  29 /* Parses 's' as a 16-digit hexadecimal number representing a datapath ID.  On
  30  * success stores the dpid into '*dpidp' and returns true, on failure stores 0
  31  * into '*dpidp' and returns false.
  32  *
  33  * Rejects an all-zeros dpid as invalid. */
  34 bool
  35 dpid_from_string(const char *s, uint64_t *dpidp)
  36 {
  37     *dpidp = (strlen(s) == 16 && strspn(s, "0123456789abcdefABCDEF") == 16
  38               ? strtoull(s, NULL, 16)
  39               : 0);
  40     return *dpidp != 0;
  41 }
  42
  43 bool
  44 eth_addr_from_string(const char *s, uint8_t ea[ETH_ADDR_LEN])
  45 {
  46     if (sscanf(s, ETH_ADDR_SCAN_FMT, ETH_ADDR_SCAN_ARGS(ea))
  47         == ETH_ADDR_SCAN_COUNT) {
  48         return true;
  49     } else {
  50         memset(ea, 0, ETH_ADDR_LEN);
  51         return false;
  52     }
  53 }
  54
  55 /* Fills 'b' with an 802.2 SNAP packet with Ethernet source address 'eth_src',
  56  * the Nicira OUI as SNAP organization and 'snap_type' as SNAP type.  The text
  57  * string in 'tag' is enclosed as the packet payload.
  58  *
  59  * This function is used by Open vSwitch to compose packets in cases where
  60  * context is important but content doesn't (or shouldn't) matter.  For this
  61  * purpose, 'snap_type' should be a random number and 'tag' should be an
  62  * English phrase that explains the purpose of the packet.  (The English phrase
  63  * gives hapless admins running Wireshark the opportunity to figure out what's
  64  * going on.) */
  65 void
  66 compose_benign_packet(struct ofpbuf *b, const char *tag, uint16_t snap_type,
  67                       const uint8_t eth_src[ETH_ADDR_LEN])
  68 {
  69     size_t tag_size = strlen(tag) + 1;
  70     char *payload;
  71
  72     payload = snap_compose(b, eth_addr_broadcast, eth_src, 0x002320, snap_type,
  73                            tag_size + ETH_ADDR_LEN);
  74     memcpy(payload, tag, tag_size);
  75     memcpy(payload + tag_size, eth_src, ETH_ADDR_LEN);
  76 }
  77
  78 /* Modify the TCI field of 'packet', whose data must begin with an Ethernet
  79  * header.  If a VLAN tag is present, its TCI field is replaced by 'tci'.  If a
  80  * VLAN tag is not present, one is added with the TCI field set to 'tci'.
  81  *
  82  * Also sets 'packet->l2' to point to the new Ethernet header. */
  83 void
  84 eth_set_vlan_tci(struct ofpbuf *packet, ovs_be16 tci)
  85 {
  86     struct eth_header *eh = packet->data;
  87     struct vlan_eth_header *veh;
  88
  89     if (packet->size >= sizeof(struct vlan_eth_header)
  90         && eh->eth_type == htons(ETH_TYPE_VLAN)) {
  91         veh = packet->data;
  92         veh->veth_tci = tci;
  93     } else {
  94         /* Insert new 802.1Q header. */
  95         struct vlan_eth_header tmp;
  96         memcpy(tmp.veth_dst, eh->eth_dst, ETH_ADDR_LEN);
  97         memcpy(tmp.veth_src, eh->eth_src, ETH_ADDR_LEN);
  98         tmp.veth_type = htons(ETH_TYPE_VLAN);
  99         tmp.veth_tci = tci;
 100         tmp.veth_next_type = eh->eth_type;
 101
 102         veh = ofpbuf_push_uninit(packet, VLAN_HEADER_LEN);
 103         memcpy(veh, &tmp, sizeof tmp);
 104     }
 105     packet->l2 = packet->data;
 106 }
 107
 108 /* Stores the string representation of the IPv6 address 'addr' into the
 109  * character array 'addr_str', which must be at least INET6_ADDRSTRLEN
 110  * bytes long. */
 111 void
 112 format_ipv6_addr(char *addr_str, const struct in6_addr *addr)
 113 {
 114     inet_ntop(AF_INET6, addr, addr_str, INET6_ADDRSTRLEN);
 115 }
 116
 117 void
 118 print_ipv6_addr(struct ds *string, const struct in6_addr *addr)
 119 {
 120     char addr_str[INET6_ADDRSTRLEN];
 121
 122     format_ipv6_addr(addr_str, addr);
 123     ds_put_format(string, "%s", addr_str);
 124 }
 125
 126 struct in6_addr ipv6_addr_bitand(const struct in6_addr *a,
 127                                  const struct in6_addr *b)
 128 {
 129     int i;
 130     struct in6_addr dst;
 131
 132 #ifdef s6_addr32
 133     for (i=0; i<4; i++) {
 134         dst.s6_addr32[i] = a->s6_addr32[i] & b->s6_addr32[i];
 135     }
 136 #else
 137     for (i=0; i<16; i++) {
 138         dst.s6_addr[i] = a->s6_addr[i] & b->s6_addr[i];
 139     }
 140 #endif
 141
 142     return dst;
 143 }
 144
 145 /* Returns an in6_addr consisting of 'mask' high-order 1-bits and 128-N
 146  * low-order 0-bits. */
 147 struct in6_addr
 148 ipv6_create_mask(int mask)
 149 {
 150     struct in6_addr netmask;
 151     uint8_t *netmaskp = &netmask.s6_addr[0];
 152
 153     memset(&netmask, 0, sizeof netmask);
 154     while (mask > 8) {
 155         *netmaskp = 0xff;
 156         netmaskp++;
 157         mask -= 8;
 158     }
 159
 160     if (mask) {
 161         *netmaskp = 0xff << (8 - mask);
 162     }
 163
 164     return netmask;
 165 }
 166
 167 /* Given the IPv6 netmask 'netmask', returns the number of bits of the
 168  * IPv6 address that it wildcards.  'netmask' must be a CIDR netmask (see
 169  * ipv6_is_cidr()). */
 170 int
 171 ipv6_count_cidr_bits(const struct in6_addr *netmask)
 172 {
 173     int i;
 174     int count = 0;
 175     const uint8_t *netmaskp = &netmask->s6_addr[0];
 176
 177     assert(ipv6_is_cidr(netmask));
 178
 179     for (i=0; i<16; i++) {
 180         if (netmaskp[i] == 0xff) {
 181             count += 8;
 182         } else {
 183             uint8_t nm;
 184
 185             for(nm = netmaskp[i]; nm; nm <<= 1) {
 186                 count++;
 187             }
 188             break;
 189         }
 190
 191     }
 192
 193     return count;
 194 }
 195
 196 /* Returns true if 'netmask' is a CIDR netmask, that is, if it consists of N
 197  * high-order 1-bits and 128-N low-order 0-bits. */
 198 bool
 199 ipv6_is_cidr(const struct in6_addr *netmask)
 200 {
 201     const uint8_t *netmaskp = &netmask->s6_addr[0];
 202     int i;
 203
 204     for (i=0; i<16; i++) {
 205         if (netmaskp[i] != 0xff) {
 206             uint8_t x = ~netmaskp[i];
 207             if (x & (x + 1)) {
 208                 return false;
 209             }
 210             while (++i < 16) {
 211                 if (netmaskp[i]) {
 212                     return false;
 213                 }
 214             }
 215         }
 216     }
 217
 218     return true;
 219 }
 220
 221 /* Populates 'b' with an Ethernet II packet headed with the given 'eth_dst',
 222  * 'eth_src' and 'eth_type' parameters.  A payload of 'size' bytes is allocated
 223  * in 'b' and returned.  This payload may be populated with appropriate
 224  * information by the caller.
 225  *
 226  * The returned packet has enough headroom to insert an 802.1Q VLAN header if
 227  * desired. */
 228 void *
 229 eth_compose(struct ofpbuf *b, const uint8_t eth_dst[ETH_ADDR_LEN],
 230             const uint8_t eth_src[ETH_ADDR_LEN], uint16_t eth_type,
 231             size_t size)
 232 {
 233     void *data;
 234     struct eth_header *eth;
 235
 236     ofpbuf_clear(b);
 237
 238     ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + VLAN_HEADER_LEN + size);
 239     ofpbuf_reserve(b, VLAN_HEADER_LEN);
 240     eth = ofpbuf_put_uninit(b, ETH_HEADER_LEN);
 241     data = ofpbuf_put_uninit(b, size);
 242
 243     memcpy(eth->eth_dst, eth_dst, ETH_ADDR_LEN);
 244     memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
 245     eth->eth_type = htons(eth_type);
 246
 247     return data;
 248 }
 249
 250 /* Populates 'b' with an Ethernet LLC+SNAP packet headed with the given
 251  * 'eth_dst', 'eth_src', 'snap_org', and 'snap_type'.  A payload of 'size'
 252  * bytes is allocated in 'b' and returned.  This payload may be populated with
 253  * appropriate information by the caller.
 254  *
 255  * The returned packet has enough headroom to insert an 802.1Q VLAN header if
 256  * desired. */
 257 void *
 258 snap_compose(struct ofpbuf *b, const uint8_t eth_dst[ETH_ADDR_LEN],
 259              const uint8_t eth_src[ETH_ADDR_LEN],
 260              unsigned int oui, uint16_t snap_type, size_t size)
 261 {
 262     struct eth_header *eth;
 263     struct llc_snap_header *llc_snap;
 264     void *payload;
 265
 266     /* Compose basic packet structure.  (We need the payload size to stick into
 267      * the 802.2 header.) */
 268     ofpbuf_clear(b);
 269     ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + VLAN_HEADER_LEN
 270                              + LLC_SNAP_HEADER_LEN + size);
 271     ofpbuf_reserve(b, VLAN_HEADER_LEN);
 272     eth = ofpbuf_put_zeros(b, ETH_HEADER_LEN);
 273     llc_snap = ofpbuf_put_zeros(b, LLC_SNAP_HEADER_LEN);
 274     payload = ofpbuf_put_uninit(b, size);
 275
 276     /* Compose 802.2 header. */
 277     memcpy(eth->eth_dst, eth_dst, ETH_ADDR_LEN);
 278     memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
 279     eth->eth_type = htons(b->size - ETH_HEADER_LEN);
 280
 281     /* Compose LLC, SNAP headers. */
 282     llc_snap->llc.llc_dsap = LLC_DSAP_SNAP;
 283     llc_snap->llc.llc_ssap = LLC_SSAP_SNAP;
 284     llc_snap->llc.llc_cntl = LLC_CNTL_SNAP;
 285     llc_snap->snap.snap_org[0] = oui >> 16;
 286     llc_snap->snap.snap_org[1] = oui >> 8;
 287     llc_snap->snap.snap_org[2] = oui;
 288     llc_snap->snap.snap_type = htons(snap_type);
 289
 290     return payload;
 291 }