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Calculate checksums correctly when LSRR is in effect by passing the

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IP header and protocol header seperately.
Also calculate TCP checksums.

Submitted by:	orion
This commit is contained in:
fenner 2002-07-28 02:34:39 +00:00
parent 5db809b70f
commit 1ef08a8805
1 changed files with 36 additions and 24 deletions
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60
contrib/traceroute/traceroute.c
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@ -222,6 +222,7 @@ static const char rcsid[] =
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netinet/tcp.h>
#include <netinet/tcpip.h>
#include <arpa/inet.h>
@ -300,7 +301,6 @@ struct outdata {
u_char seq; /* sequence number of this packet */
u_char ttl; /* ttl packet left with */
struct timeval tv; /* time packet left */
int optlen; /* length of ip options */
};
#ifndef HAVE_ICMP_NEXTMTU
@ -366,6 +366,7 @@ struct hostinfo *gethostinfo(char *);
u_short in_cksum(u_short *, int);
char *inetname(struct in_addr);
int main(int, char **);
u_short p_cksum(struct ip *, u_short *, int);
int packet_ok(u_char *, int, struct sockaddr_in *, int);
char *pr_type(u_char);
void print(u_char *, int, struct sockaddr_in *);
@ -470,7 +471,6 @@ main(int argc, char **argv)
register u_short off = 0;
struct ifaddrlist *al;
char errbuf[132];
register int optlen = 0;
int requestPort = -1;
int sump = 0;
int sockerrno;
@ -924,7 +924,6 @@ main(int argc, char **argv)
/* Prepare outgoing data */
outdata.seq = ++seq;
outdata.ttl = ttl;
outdata.optlen = optlen;
/* Avoid alignment problems by copying bytewise: */
(void)gettimeofday(&t1, &tz);
@ -1269,13 +1268,10 @@ icmp_prep(struct outdata *outdata)
icmpheader->icmp_type = ICMP_ECHO;
icmpheader->icmp_id = htons(ident);
icmpheader->icmp_seq = htons(outdata->seq);
icmpheader->icmp_cksum = 0;
icmpheader->icmp_cksum = in_cksum((u_short *)icmpheader,
packlen - (sizeof(*outip) + outdata->optlen));
icmpheader->icmp_cksum = in_cksum((u_short *)icmpheader, protlen);
if (icmpheader->icmp_cksum == 0)
icmpheader->icmp_cksum = 0xffff;
}
int
@ -1291,29 +1287,17 @@ void
udp_prep(struct outdata *outdata)
{
struct udphdr *const outudp = (struct udphdr *) outp;
struct ip tip;
struct udpiphdr *ui, *oui;
outudp->uh_sport = htons(ident);
outudp->uh_dport = htons(port + outdata->seq);
outudp->uh_ulen = htons((u_short)protlen);
outudp->uh_sum = 0;
if (doipcksum) {
/* Checksum (we must save and restore ip header) */
tip = *outip;
ui = (struct udpiphdr *)outip;
oui = (struct udpiphdr *)&tip;
/* Easier to zero and put back things that are ok */
memset((char *)ui, 0, sizeof(ui->ui_i));
ui->ui_src = oui->ui_src;
ui->ui_dst = oui->ui_dst;
ui->ui_pr = oui->ui_pr;
ui->ui_len = outudp->uh_ulen;
outudp->uh_sum = 0;
outudp->uh_sum = in_cksum((u_short *)ui, packlen);
if (outudp->uh_sum == 0)
outudp->uh_sum = 0xffff;
*outip = tip;
u_short sum = p_cksum(outip, (u_short*)outudp, protlen);
outudp->uh_sum = (sum) ? sum : 0xffff;
}
return;
}
int
@ -1336,6 +1320,12 @@ tcp_prep(struct outdata *outdata)
tcp->th_ack = 0;
tcp->th_off = 5;
tcp->th_flags = TH_SYN;
tcp->th_sum = 0;
if (doipcksum) {
u_short sum = p_cksum(outip, (u_short*)tcp, protlen);
tcp->th_sum = (sum) ? sum : 0xffff;
}
}
int
@ -1405,6 +1395,28 @@ print(register u_char *buf, register int cc, register struct sockaddr_in *from)
Printf(" %d bytes to %s", cc, inet_ntoa (ip->ip_dst));
}
/*
* Checksum routine for UDP and TCP headers.
*/
u_short
p_cksum(struct ip *ip, u_short *data, int len)
{
static struct ipovly ipo;
u_short sumh, sumd;
u_long sumt;
ipo.ih_pr = ip->ip_p;
ipo.ih_len = htons(len);
ipo.ih_src = ip->ip_src;
ipo.ih_dst = ip->ip_dst;
sumh = in_cksum((u_short*)&ipo, sizeof(ipo)); /* pseudo ip hdr cksum */
sumd = in_cksum((u_short*)data, len); /* payload data cksum */
sumt = (sumh << 16) | (sumd);
return ~in_cksum((u_short*)&sumt, sizeof(sumt));
}
/*
* Checksum routine for Internet Protocol family headers (C Version)
*/