fluffy/p4split.c

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2.7 KiB
C
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#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <sysexits.h>
#include <strings.h>
#include "pcap.h"
/* Gaah so much crap */
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/ether.h>
#include <netinet/ip.h>
#include <netinet/in.h>
int
usage(int ret)
{
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fprintf(stderr, "Usage: p4split CIDR\n");
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fprintf(stderr, "\n");
fprintf(stderr, "Splits pcap on stdin into up to 256 files, based on CIDR.\n");
return ret;
}
int
parse_cidr(char *s, uint32_t *addr, uint8_t *bits)
{
char *slash = index(s, '/');
struct in_addr inp;
if (slash) {
*slash = 0;
*bits = atoi(slash + 1);
} else {
*bits = 0;
}
if (0 == inet_aton(s, &inp)) return -1;
*addr = ntohl(inp.s_addr);
return 0;
}
int
main(int argc, char *argv[])
{
struct pcap_file p;
struct pcap_file out[256];
int ok = 0;
uint32_t addr;
uint32_t mask;
uint8_t bits;
uint8_t shr;
int i;
if (argc != 2) return usage(0);
if (-1 == parse_cidr(argv[1], &addr, &bits)) return usage(0);
if (bits > 24) return usage(0);
if (bits % 8) {
fprintf(stderr, "Warning: routing prefix is not a multiple of 8.\n");
}
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mask = ~((1 << (32-bits)) - 1);
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addr &= mask;
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shr = (32-bits) - 8;
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for (i = 0; i < 256; i += 1) {
out[i].f = NULL;
}
if (-1 == pcap_open_in(&p, stdin)) return usage(0);
while (1) {
struct pcap_pkthdr hdr;
uint8_t octet;
char frame[MAXFRAME];
ok = 1;
if (-1 == pcap_read_pkthdr(&p, &hdr)) break;
if (1 != fread(frame, hdr.caplen, 1, p.f)) break;
{
struct ether_header *eh = (struct ether_header *)frame;
struct iphdr *ih = (struct iphdr *)(frame + sizeof(struct ether_header));
uint32_t a;
/* VLAN tag */
if (ntohs(eh->ether_type) == 0x8100) {
ih = (struct iphdr *)((char *)ih + 4);
}
a = ntohl(ih->saddr);
if ((a & mask) != addr) {
a = ntohl(ih->daddr);
if ((a & mask) != addr) {
fprintf(stderr, "Warning: dropping unmatched packet %08x -> %08x\n",
ntohl(ih->saddr), ntohl(ih->daddr));
continue;
}
}
octet = (a & ~mask) >> shr;
}
ok = 0;
if (! out[octet].f) {
char fn[9];
FILE *f;
sprintf(fn, "%d.pcap", octet);
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if (NULL == (f = fopen(fn, "wb"))) break;
if (-1 == pcap_open_out(&out[octet], f)) break;
}
if (-1 == pcap_write_pkthdr(&out[octet], &hdr)) break;
if (1 != fwrite(frame, hdr.caplen, 1, out[octet].f)) break;
}
if (! ok) {
perror("Error");
return 1;
}
for (i = 0; i < 256; i += 1) {
if (out[i].f) {
pcap_close(&p);
}
}
return 0;
}