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started fixing TCP checksum claculation n

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This commit is contained in:
Steffen Vogel 2017-12-20 10:17:48 +01:00
parent cf998a2856
commit 764a5e570b
1 changed files with 53 additions and 24 deletions
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77
probe.c
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@ -37,47 +37,72 @@
#include "utils.h"
#include "hist.h"
int probe_tcp(int sd, unsigned short dport, struct timespec *ts)
struct phdr {
struct in_addr source;
struct in_addr destination;
uint8_t reserved;
uint8_t protocol;
uint16_t length;
} __attribute__((packed));
int probe_tcp(int sd, unsigned short dport, struct in_addr src, struct in_addr dst, struct timespec *ts)
{
struct timespec ts_syn, ts_ack;
struct iphdr ihdr;
struct tcphdr thdr;
struct phdr *phdr;
struct iphdr *ihdr;
struct tcphdr *thdr;
char buf[sizeof(struct phdr) + sizeof(struct iphdr) + sizeof(struct tcphdr)];
struct msghdr msgh;
ssize_t len;
struct iovec iov[2] = {
{ .iov_base = &ihdr, .iov_len = sizeof(ihdr) }, // IP header
{ .iov_base = &thdr, .iov_len = sizeof(thdr) } // TCP header
};
/* Sending SYN */
memset(&ihdr, 0, sizeof(ihdr));
memset(&thdr, 0, sizeof(thdr));
memset(buf, 0, sizeof(buf));
memset(&msgh, 0, sizeof(msgh));
/* 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(sport);
thdr.dest = htons(dport);
thdr.doff = 5;
thdr.check = tcp_csum((unsigned short *) &thdr, sizeof(thdr));
phdr = (struct phdr *) buf;
thdr = (struct tcphdr *) (phdr + 1);
msgh.msg_iov = &iov[1]; // only send TCP header
phdr->source = src;
phdr->destination = dst;
phdr->protocol = IPPROTO_TCP;
phdr->length = sizeof(struct tcphdr);
thdr->syn = 1;
thdr->seq = htonl(seq);
thdr->source = htons(sport);
thdr->dest = htons(dport);
thdr->doff = 5;
thdr->check = tcp_csum((unsigned short *) &phdr, sizeof(struct phdr) + sizeof(struct tcphdr));
struct iovec iov1[] = {
{ .iov_base = thdr, .iov_len = sizeof(struct tcphdr) } // TCP header
};
msgh.msg_iov = iov1; // only send TCP header
msgh.msg_iovlen = 1;
if (ts_sendmsg(sd, &msgh, 0, &ts_syn) < 0)
error(-1, errno, "Failed to send SYN packet");
/* Receiving ACK */
memset(&ihdr, 0, sizeof(ihdr));
memset(&thdr, 0, sizeof(thdr));
memset(buf, 0, sizeof(buf));
msgh.msg_iov = &iov[0]; // receive IP + TCP header
ihdr = (struct iphdr *) buf;
thdr = (struct tcphdr *) (ihdr + 1);
struct iovec iov2[] = {
{ .iov_base = ihdr, .iov_len = sizeof(struct iphdr) }, // IP header
{ .iov_base = thdr, .iov_len = sizeof(struct tcphdr) } // TCP header
};
msgh.msg_iov = iov2; // receive IP + TCP header
msgh.msg_iovlen = 2;
retry: len = ts_recvmsg(sd, &msgh, 0, &ts_ack);
@ -88,15 +113,15 @@ 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(dport) || thdr.dest != htons(sport)) {
if (thdr->source != htons(dport) || thdr->dest != htons(sport)) {
printf("Skipping invalid ports\n");
goto retry;
}
else if (!thdr.rst && !(thdr.ack && thdr.syn)) {
else if (!thdr->rst && !(thdr->ack && thdr->syn)) {
printf("Skipping invalid flags\n");
goto retry;
}
else if (ntohl(thdr.ack_seq) != seq + 1) {
else if (ntohl(thdr->ack_seq) != seq + 1) {
printf("Skipping invalid seq\n");
goto retry;
}
@ -113,6 +138,7 @@ int probe(int argc, char *argv[])
/* Parse address */
struct nl_addr *addr;
struct sockaddr_in sin;
struct in_addr src, dst;
/* Parse args */
if (argc != 2)
@ -129,6 +155,9 @@ int probe(int argc, char *argv[])
if (nl_addr_fill_sockaddr(addr, (struct sockaddr *) &sin, &sinlen))
error(-1, 0, "Failed to fill sockaddr");
dst = sin.sin_addr;
inet_aton("134.130.169.31", &src);
/* Create RAW socket */
int sd = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
if (sd < 0)
@ -156,7 +185,7 @@ int probe(int argc, char *argv[])
error(-1, errno, "Failed to initilize timer");
do {
probe_tcp(sd, dport, &ts);
probe_tcp(sd, dport, src, dst, &ts);
double rtt = time_to_double(&ts);
hist_put(&hist, rtt);