fluffy/pcap.c

#include <stdio.h>
#include <sysexits.h>
#include <string.h>
#include "pcap.h"

int
pcap_open_in(struct pcap_file *ctx, FILE *f)
{
  struct pcap_file_header h;

  if (1 != fread(&h, sizeof(h), 1, f)) {
    h.magic = 0;
  }

  if (MAGIC == h.magic) {
    ctx->swap = 0;
  } else if (bswap32(MAGIC) == h.magic) {
    ctx->swap = 1;
  } else {
    return -1;
  }
  if ((h.version_major != 2) || (h.version_minor != 4)) return -1;

  if (ctx->swap) h.snaplen = bswap32(h.snaplen);
  if (h.snaplen > MAXFRAME) return -1;

  ctx->f = f;
  return 0;
}

int
pcap_open_out(struct pcap_file *ctx, FILE *f)
{
  struct pcap_file_header h = { MAGIC, 2, 4, 0, 0, MAXFRAME, 1 };

  if (1 != fwrite(&h, sizeof(h), 1, f)) return -1;
  ctx->f = f;
  ctx->swap = 0;

  return 0;
}

int
pcap_read_pkthdr(struct pcap_file *ctx, struct pcap_pkthdr *hdr)
{
  if (1 != fread(hdr, sizeof(*hdr), 1, ctx->f)) {
    return -1;
  }

  if (ctx->swap) {
    hdr->ts.tv_sec  = bswap32(hdr->ts.tv_sec);
    hdr->ts.tv_usec = bswap32(hdr->ts.tv_usec);
    hdr->caplen     = bswap32(hdr->caplen);
    hdr->len        = bswap32(hdr->len);
  }

  if (hdr->caplen > MAXFRAME) return -1;

  return 0;
}

int
pcap_write_pkthdr(struct pcap_file *ctx, struct pcap_pkthdr *hdr)
{
  if (ctx->swap) {
    struct pcap_pkthdr ohdr;

    memcpy(&ohdr, hdr, sizeof(ohdr));
    hdr->ts.tv_sec  = bswap32(hdr->ts.tv_sec);
    hdr->ts.tv_usec = bswap32(hdr->ts.tv_usec);
    hdr->caplen     = bswap32(hdr->caplen);
    hdr->len        = bswap32(hdr->len);

    if (1 != fwrite(&ohdr, sizeof(ohdr), 1, ctx->f)) return -1;
  } else {
    if (1 != fwrite(hdr, sizeof(*hdr), 1, ctx->f)) return -1;
  }

  return 0;
}

void
pcap_close(struct pcap_file *ctx)
{
  fclose(ctx->f);
}