lib/pcap-file.c

   1 /*
   2  * Copyright (c) 2009, 2010, 2012 Nicira, Inc.
   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 "pcap-file.h"
  19 #include <errno.h>
  20 #include <inttypes.h>
  21 #include <string.h>
  22 #include "compiler.h"
  23 #include "ofpbuf.h"
  24 #include "vlog.h"
  25
  26 VLOG_DEFINE_THIS_MODULE(pcap);
  27
  28 struct pcap_hdr {
  29     uint32_t magic_number;   /* magic number */
  30     uint16_t version_major;  /* major version number */
  31     uint16_t version_minor;  /* minor version number */
  32     int32_t thiszone;        /* GMT to local correction */
  33     uint32_t sigfigs;        /* accuracy of timestamps */
  34     uint32_t snaplen;        /* max length of captured packets */
  35     uint32_t network;        /* data link type */
  36 };
  37 BUILD_ASSERT_DECL(sizeof(struct pcap_hdr) == 24);
  38
  39 struct pcaprec_hdr {
  40     uint32_t ts_sec;         /* timestamp seconds */
  41     uint32_t ts_usec;        /* timestamp microseconds */
  42     uint32_t incl_len;       /* number of octets of packet saved in file */
  43     uint32_t orig_len;       /* actual length of packet */
  44 };
  45 BUILD_ASSERT_DECL(sizeof(struct pcaprec_hdr) == 16);
  46
  47 FILE *
  48 pcap_open(const char *file_name, const char *mode)
  49 {
  50     FILE *file;
  51
  52     ovs_assert(!strcmp(mode, "rb") || !strcmp(mode, "wb"));
  53
  54     file = fopen(file_name, mode);
  55     if (file == NULL) {
  56         VLOG_WARN("%s: failed to open pcap file for %s",
  57                   file_name, mode[0] == 'r' ? "reading" : "writing");
  58         return NULL;
  59     }
  60
  61     if (mode[0] == 'r') {
  62         if (!pcap_read_header(file)) {
  63             fclose(file);
  64             return NULL;
  65         }
  66     } else {
  67         pcap_write_header(file);
  68     }
  69     return file;
  70 }
  71
  72 int
  73 pcap_read_header(FILE *file)
  74 {
  75     struct pcap_hdr ph;
  76     if (fread(&ph, sizeof ph, 1, file) != 1) {
  77         int error = ferror(file) ? errno : EOF;
  78         VLOG_WARN("failed to read pcap header: %s", ovs_retval_to_string(error));
  79         return error;
  80     }
  81     if (ph.magic_number != 0xa1b2c3d4 && ph.magic_number != 0xd4c3b2a1) {
  82         VLOG_WARN("bad magic 0x%08"PRIx32" reading pcap file "
  83                   "(expected 0xa1b2c3d4 or 0xd4c3b2a1)", ph.magic_number);
  84         return EPROTO;
  85     }
  86     return 0;
  87 }
  88
  89 void
  90 pcap_write_header(FILE *file)
  91 {
  92     /* The pcap reader is responsible for figuring out endianness based on the
  93      * magic number, so the lack of htonX calls here is intentional. */
  94     struct pcap_hdr ph;
  95     ph.magic_number = 0xa1b2c3d4;
  96     ph.version_major = 2;
  97     ph.version_minor = 4;
  98     ph.thiszone = 0;
  99     ph.sigfigs = 0;
 100     ph.snaplen = 1518;
 101     ph.network = 1;             /* Ethernet */
 102     ignore(fwrite(&ph, sizeof ph, 1, file));
 103 }
 104
 105 int
 106 pcap_read(FILE *file, struct ofpbuf **bufp)
 107 {
 108     struct pcaprec_hdr prh;
 109     struct ofpbuf *buf;
 110     void *data;
 111     size_t len;
 112
 113     *bufp = NULL;
 114
 115     /* Read header. */
 116     if (fread(&prh, sizeof prh, 1, file) != 1) {
 117         if (ferror(file)) {
 118             int error = errno;
 119             VLOG_WARN("failed to read pcap record header: %s",
 120                       ovs_retval_to_string(error));
 121             return error;
 122         } else {
 123             return EOF;
 124         }
 125     }
 126
 127     /* Calculate length. */
 128     len = prh.incl_len;
 129     if (len > 0xffff) {
 130         uint32_t swapped_len = (((len & 0xff000000) >> 24) |
 131                                 ((len & 0x00ff0000) >>  8) |
 132                                 ((len & 0x0000ff00) <<  8) |
 133                                 ((len & 0x000000ff) << 24));
 134         if (swapped_len > 0xffff) {
 135             VLOG_WARN("bad packet length %zu or %"PRIu32" "
 136                       "reading pcap file",
 137                       len, swapped_len);
 138             return EPROTO;
 139         }
 140         len = swapped_len;
 141     }
 142
 143     /* Read packet. */
 144     buf = ofpbuf_new(len);
 145     data = ofpbuf_put_uninit(buf, len);
 146     if (fread(data, len, 1, file) != 1) {
 147         int error = ferror(file) ? errno : EOF;
 148         VLOG_WARN("failed to read pcap packet: %s",
 149                   ovs_retval_to_string(error));
 150         ofpbuf_delete(buf);
 151         return error;
 152     }
 153     *bufp = buf;
 154     return 0;
 155 }
 156
 157 void
 158 pcap_write(FILE *file, struct ofpbuf *buf)
 159 {
 160     struct pcaprec_hdr prh;
 161     prh.ts_sec = 0;
 162     prh.ts_usec = 0;
 163     prh.incl_len = buf->size;
 164     prh.orig_len = buf->size;
 165     ignore(fwrite(&prh, sizeof prh, 1, file));
 166     ignore(fwrite(buf->data, buf->size, 1, file));
 167 }