netbuf_t
pppgetbuf(netif_t ifp)
{
NETBUF_T nb;
int len = MAX(if_mtu(ifp), PPP_MTU) + PPP_HDRLEN + PPP_FCSLEN;
nb = NB_ALLOC(len);
if (nb != NULL)
{
NB_SHRINK_TOP(nb, PPP_HDRLEN);
NB_SHRINK_BOT(nb, PPP_FCSLEN); /* grown by pppstart() */
}
return NB_TO_nb(nb);
}
int
main(int argc, char *argv[])
{
char pkt[IP_MAXPACKET];
ssize_t pktlen, hlen;
struct ip *pip = (struct ip *)pkt;
struct sockaddr_in sin;
socklen_t sinlen;
int s;
int mflag;
u_long mtu;
u_int16_t maxmss;
int rtsock;
int ifindex;
int pflag;
u_short port;
int ch;
fd_set fdset;
mflag = pflag = 0;
port = 0; /* XXX gcc -Wuninitialized */
ifindex = 0;
rtsock = -1;
while ((ch = getopt(argc, argv, "bi:m:p:v")) != -1)
switch (ch) {
case 'b':
both = 1;
break;
case 'i':
if (!(ifindex = if_mtu(optarg, &mtu))) {
errx(1, "unknown interface %s", optarg);
/* NOTREACHED */
}
snprintf(pidfilename, sizeof pidfilename,
"%stcpmssd.%s.pid", _PATH_VARRUN, optarg);
break;
case 'm':
if ((mtu = atoi(optarg)) < 68) {
errx(1, "invalid MTU value");
/* NOTREACHED */
}
mflag++;
break;
case 'p':
port = htons(atoi(optarg));
pflag++;
break;
case 'v':
verbose = 1;
break;
case '?':
default:
usage();
/* NOTREACHED */
}
argc -= optind;
argv += optind;
if (!(!mflag - !ifindex) || !pflag || argc) {
usage();
/* NOTREACHED */
}
if ((s = socket(PF_INET, SOCK_RAW, IPPROTO_DIVERT)) == -1) {
err(1, "can't create divert socket");
/* NOTREACHED */
}
bzero(&sin, sizeof(sin));
sin.sin_family = PF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
sin.sin_port = port;
if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) == -1) {
err(1, "can't bind divert socket");
/* NOTREACHED */
}
if (ifindex)
if ((rtsock = socket(PF_ROUTE, SOCK_RAW, 0)) == -1) {
err(1, "can't create routing socket");
/* NOTREACHED */
}
maxmss = MAXMSS(mtu);
if (verbose)
fprintf(stderr, "Maximum MSS: %u\n", maxmss);
if (!verbose)
if (daemon(0, 0) == -1) {
err(1, "can't daemonize");
/* NOTREACHED */
}
if (ifindex) {
FILE *pidfile;
pidfile = fopen(pidfilename, "w");
if (pidfile != NULL) {
fprintf(pidfile, "%d\n", (int)getpid());
fclose(pidfile);
if (signal(SIGTERM, sigterm_handler) == SIG_ERR) {
err(1, "can't install SIGTERM handler");
/* NOTREACHED */
}
}
}
while (1) {
FD_ZERO(&fdset);
FD_SET(s, &fdset);
if (rtsock != -1)
FD_SET(rtsock, &fdset);
if (select(32, &fdset, (fd_set *)NULL, (fd_set *)NULL, (struct timeval *)NULL) == -1) {
warn("select failed");
continue;
}
if (rtsock != -1 && FD_ISSET(rtsock, &fdset)) {
struct if_msghdr ifm;
if ((pktlen = read(rtsock, &ifm, sizeof(ifm))) == -1) {
warn("read from routing socket failed");
continue;
}
if (ifm.ifm_version != RTM_VERSION) {
if (verbose)
warnx("routing message version %d "
"not understood", ifm.ifm_version);
continue;
}
if (ifm.ifm_type != RTM_IFINFO ||
ifm.ifm_index != ifindex)
continue;
if (mtu != ifm.ifm_data.ifi_mtu) {
mtu = ifm.ifm_data.ifi_mtu;
maxmss = MAXMSS(mtu);
if (verbose)
fprintf(stderr, "Maximum MSS: %u\n", maxmss);
}
}
if (FD_ISSET(s, &fdset)) {
sinlen = sizeof(sin);
if ((pktlen = recvfrom(s, pkt, sizeof(pkt), 0,
(struct sockaddr *)&sin, &sinlen)) == -1)
if (errno != EINTR) {
warn("read from divert socket failed");
continue;
}
hlen = pip->ip_hl << 2;
/*-
* Check for MSS option only for outgoing
* TCP packets with zero fragment offset
* and correct total and header lengths.
*/
if ((both || sin.sin_addr.s_addr == INADDR_ANY) &&
pip->ip_p == IPPROTO_TCP &&
(ntohs(pip->ip_off) & IP_OFFMASK) == 0 &&
ntohs(pip->ip_len) == pktlen &&
hlen <= pktlen &&
pktlen - hlen >= sizeof(struct tcphdr))
correct_mss((struct tcphdr *)(pkt + hlen),
pktlen - hlen, maxmss);
if (sendto(s, pkt, pktlen, 0,
(struct sockaddr *)&sin, sinlen) == -1)
warn("write to divert socket failed");
}
}
}
