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randomize source port

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This commit is contained in:
Steffen Vogel 2015-07-20 16:06:45 +02:00
parent 8cfe47afb5
commit fda10984ed
2 changed files with 13 additions and 12 deletions
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3
config.h
View file

@ -10,9 +10,6 @@
#define VERSION "0.1"
#define SRC_PORT 23532
#define DEST_PORT 22
struct config {
int mark;
int mask;

22
probe.c
View file

@ -36,7 +36,7 @@
#include "utils.h"
#include "hist.h"
int probe_tcp(int sd, struct timespec *ts)
int probe_tcp(int sd, unsigned short dport, struct timespec *ts)
{
struct timespec ts_syn, ts_ack;
@ -55,12 +55,14 @@ int probe_tcp(int sd, struct timespec *ts)
memset(&thdr, 0, sizeof(thdr));
memset(&msgh, 0, sizeof(msgh));
unsigned seq = (unsigned) rand();
/* Randomize sequence number and source port */
unsigned int seq = (unsigned) rand();
unsigned short sport = (rand() + 1024) & 0xFFFF;
thdr.syn = 1;
thdr.seq = htonl(seq);
thdr.source = htons(SRC_PORT);
thdr.dest = htons(DEST_PORT);
thdr.source = htons(sport);
thdr.dest = htons(dport);
thdr.doff = 5;
thdr.check = tcp_csum((unsigned short *) &thdr, sizeof(thdr));
@ -85,7 +87,7 @@ retry: len = ts_recvmsg(sd, &msgh, 0, &ts_ack);
// len, thdr.syn, thdr.ack, thdr.rst, ntohl(thdr.seq), ntohl(thdr.ack_seq), ntohs(thdr.source), ntohs(thdr.dest));
/* Check response */
if (thdr.source != htons(DEST_PORT) || thdr.dest != htons(SRC_PORT)) {
if (thdr.source != htons(dport) || thdr.dest != htons(sport)) {
printf("Skipping invalid ports\n");
goto retry;
}
@ -108,15 +110,17 @@ int probe(int argc, char *argv[])
/* Parse address */
struct nl_addr *addr;
struct sockaddr_in sin;
char buf[128];
if (argc != 1)
error(-1, 0, "usage: netem probe IP-ADDRESS");
/* Parse args */
if (argc != 2)
error(-1, 0, "usage: netem probe IP PORT");
if (nl_addr_parse(argv[0], AF_UNSPEC, &addr))
error(-1, 0, "Failed to parse address: %s", argv[0]);
printf("Start probing: %s\n", nl_addr2str(addr, buf, sizeof(buf)));
unsigned short dport = atoi(argv[1]);
if (!dport)
error(-1, 0, "Failed to parse port: %s", argv[1]);
socklen_t sinlen = sizeof(sin);
if (nl_addr_fill_sockaddr(addr, (struct sockaddr *) &sin, &sinlen))