static int
protohandlerin(struct libalias *la, struct ip *pip, struct alias_data *ah)
{
AliasHandlePptpIn(la, pip, ah->lnk);
return (0);
}
static int
TcpAliasIn(struct ip *pip)
{
struct tcphdr *tc;
struct alias_link *link;
tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
link = FindUdpTcpIn(pip->ip_src, pip->ip_dst,
tc->th_sport, tc->th_dport,
IPPROTO_TCP,
!(packetAliasMode & PKT_ALIAS_PROXY_ONLY));
if (link != NULL)
{
struct in_addr alias_address;
struct in_addr original_address;
struct in_addr proxy_address;
u_short alias_port;
u_short proxy_port;
int accumulate;
u_short *sptr;
/* Special processing for IP encoding protocols */
if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER
|| ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER)
AliasHandlePptpIn(pip, link);
alias_address = GetAliasAddress(link);
original_address = GetOriginalAddress(link);
proxy_address = GetProxyAddress(link);
alias_port = tc->th_dport;
tc->th_dport = GetOriginalPort(link);
proxy_port = GetProxyPort(link);
/* Adjust TCP checksum since destination port is being unaliased */
/* and destination port is being altered. */
accumulate = alias_port;
accumulate -= tc->th_dport;
sptr = (u_short *) &alias_address;
accumulate += *sptr++;
accumulate += *sptr;
sptr = (u_short *) &original_address;
accumulate -= *sptr++;
accumulate -= *sptr;
/* If this is a proxy, then modify the TCP source port and
checksum accumulation */
if (proxy_port != 0)
{
accumulate += tc->th_sport;
tc->th_sport = proxy_port;
accumulate -= tc->th_sport;
sptr = (u_short *) &pip->ip_src;
accumulate += *sptr++;
accumulate += *sptr;
sptr = (u_short *) &proxy_address;
accumulate -= *sptr++;
accumulate -= *sptr;
}
/* See if ACK number needs to be modified */
if (GetAckModified(link) == 1)
{
int delta;
delta = GetDeltaAckIn(pip, link);
if (delta != 0)
{
sptr = (u_short *) &tc->th_ack;
accumulate += *sptr++;
accumulate += *sptr;
tc->th_ack = htonl(ntohl(tc->th_ack) - delta);
sptr = (u_short *) &tc->th_ack;
accumulate -= *sptr++;
accumulate -= *sptr;
}
}
ADJUST_CHECKSUM(accumulate, tc->th_sum);
/* Restore original IP address */
sptr = (u_short *) &pip->ip_dst;
accumulate = *sptr++;
accumulate += *sptr;
pip->ip_dst = original_address;
sptr = (u_short *) &pip->ip_dst;
accumulate -= *sptr++;
accumulate -= *sptr;
/* If this is a transparent proxy packet, then modify the source
address */
if (proxy_address.s_addr != 0)
{
sptr = (u_short *) &pip->ip_src;
accumulate += *sptr++;
accumulate += *sptr;
pip->ip_src = proxy_address;
sptr = (u_short *) &pip->ip_src;
accumulate -= *sptr++;
accumulate -= *sptr;
}
ADJUST_CHECKSUM(accumulate, pip->ip_sum);
/* Monitor TCP connection state */
TcpMonitorIn(pip, link);
return(PKT_ALIAS_OK);
}
return(PKT_ALIAS_IGNORED);
}
