lib/packets.c

   1 /*
   2  * Copyright (c) 2009, 2010 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     struct eth_header *eth;
  70     struct llc_snap_header *llc_snap;
  71
  72     /* Compose basic packet structure.  (We need the payload size to stick into
  73      * the 802.2 header.) */
  74     ofpbuf_clear(b);
  75     eth = ofpbuf_put_zeros(b, ETH_HEADER_LEN);
  76     llc_snap = ofpbuf_put_zeros(b, LLC_SNAP_HEADER_LEN);
  77     ofpbuf_put(b, tag, strlen(tag) + 1); /* Includes null byte. */
  78     ofpbuf_put(b, eth_src, ETH_ADDR_LEN);
  79
  80     /* Compose 802.2 header. */
  81     memcpy(eth->eth_dst, eth_addr_broadcast, ETH_ADDR_LEN);
  82     memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
  83     eth->eth_type = htons(b->size - ETH_HEADER_LEN);
  84
  85     /* Compose LLC, SNAP headers. */
  86     llc_snap->llc.llc_dsap = LLC_DSAP_SNAP;
  87     llc_snap->llc.llc_ssap = LLC_SSAP_SNAP;
  88     llc_snap->llc.llc_cntl = LLC_CNTL_SNAP;
  89     memcpy(llc_snap->snap.snap_org, "\x00\x23\x20", 3);
  90     llc_snap->snap.snap_type = htons(snap_type);
  91 }
  92
  93 /* Stores the string representation of the IPv6 address 'addr' into the
  94  * character array 'addr_str', which must be at least INET6_ADDRSTRLEN
  95  * bytes long. */
  96 void
  97 format_ipv6_addr(char *addr_str, const struct in6_addr *addr)
  98 {
  99     inet_ntop(AF_INET6, addr, addr_str, INET6_ADDRSTRLEN);
 100 }
 101
 102 void
 103 print_ipv6_addr(struct ds *string, const struct in6_addr *addr)
 104 {
 105     char addr_str[INET6_ADDRSTRLEN];
 106
 107     format_ipv6_addr(addr_str, addr);
 108     ds_put_format(string, "%s", addr_str);
 109 }
 110
 111 struct in6_addr ipv6_addr_bitand(const struct in6_addr *a,
 112                                  const struct in6_addr *b)
 113 {
 114     int i;
 115     struct in6_addr dst;
 116
 117 #ifdef s6_addr32
 118     for (i=0; i<4; i++) {
 119         dst.s6_addr32[i] = a->s6_addr32[i] & b->s6_addr32[i];
 120     }
 121 #else
 122     for (i=0; i<16; i++) {
 123         dst.s6_addr[i] = a->s6_addr[i] & b->s6_addr[i];
 124     }
 125 #endif
 126
 127     return dst;
 128 }
 129
 130 /* Returns an in6_addr consisting of 'mask' high-order 1-bits and 128-N
 131  * low-order 0-bits. */
 132 struct in6_addr
 133 ipv6_create_mask(int mask)
 134 {
 135     struct in6_addr netmask;
 136     uint8_t *netmaskp = &netmask.s6_addr[0];
 137
 138     memset(&netmask, 0, sizeof netmask);
 139     while (mask > 8) {
 140         *netmaskp = 0xff;
 141         netmaskp++;
 142         mask -= 8;
 143     }
 144
 145     if (mask) {
 146         *netmaskp = 0xff << (8 - mask);
 147     }
 148
 149     return netmask;
 150 }
 151
 152 /* Given the IPv6 netmask 'netmask', returns the number of bits of the
 153  * IPv6 address that it wildcards.  'netmask' must be a CIDR netmask (see
 154  * ipv6_is_cidr()). */
 155 int
 156 ipv6_count_cidr_bits(const struct in6_addr *netmask)
 157 {
 158     int i;
 159     int count = 0;
 160     const uint8_t *netmaskp = &netmask->s6_addr[0];
 161
 162     assert(ipv6_is_cidr(netmask));
 163
 164     for (i=0; i<16; i++) {
 165         if (netmaskp[i] == 0xff) {
 166             count += 8;
 167         } else {
 168             uint8_t nm;
 169
 170             for(nm = netmaskp[i]; nm; nm <<= 1) {
 171                 count++;
 172             }
 173             break;
 174         }
 175
 176     }
 177
 178     return count;
 179 }
 180
 181
 182 /* Returns true if 'netmask' is a CIDR netmask, that is, if it consists of N
 183  * high-order 1-bits and 128-N low-order 0-bits. */
 184 bool
 185 ipv6_is_cidr(const struct in6_addr *netmask)
 186 {
 187     const uint8_t *netmaskp = &netmask->s6_addr[0];
 188     int i;
 189
 190     for (i=0; i<16; i++) {
 191         if (netmaskp[i] != 0xff) {
 192             uint8_t x = ~netmaskp[i];
 193             if (x & (x + 1)) {
 194                 return false;
 195             }
 196             while (++i < 16) {
 197                 if (netmaskp[i]) {
 198                     return false;
 199                 }
 200             }
 201         }
 202     }
 203
 204     return true;
 205 }