static int
IcmpAliasIn1(struct libalias *la, struct ip *pip)
{
/*
De-alias incoming echo and timestamp replies.
Alias incoming echo and timestamp requests.
*/
struct alias_link *lnk;
struct icmp *ic;
LIBALIAS_LOCK_ASSERT(la);
ic = (struct icmp *)ip_next(pip);
/* Get source address from ICMP data field and restore original data */
lnk = FindIcmpIn(la, pip->ip_src, pip->ip_dst, ic->icmp_id, 1);
if (lnk != NULL) {
u_short original_id;
int accumulate;
original_id = GetOriginalPort(lnk);
/* Adjust ICMP checksum */
accumulate = ic->icmp_id;
accumulate -= original_id;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
/* Put original sequence number back in */
ic->icmp_id = original_id;
/* Put original address back into IP header */
{
struct in_addr original_address;
original_address = GetOriginalAddress(lnk);
DifferentialChecksum(&pip->ip_sum,
&original_address, &pip->ip_dst, 2);
pip->ip_dst = original_address;
}
return (PKT_ALIAS_OK);
}
return (PKT_ALIAS_IGNORED);
}
static int
IcmpAliasIn2(struct libalias *la, struct ip *pip)
{
LIBALIAS_LOCK_ASSERT(la);
/*
Alias incoming ICMP error messages containing
IP header and first 64 bits of datagram.
*/
struct ip *ip;
struct icmp *ic, *ic2;
struct udphdr *ud;
struct tcphdr *tc;
struct alias_link *lnk;
ic = (struct icmp *)ip_next(pip);
ip = &ic->icmp_ip;
ud = (struct udphdr *)ip_next(ip);
tc = (struct tcphdr *)ip_next(ip);
ic2 = (struct icmp *)ip_next(ip);
if (ip->ip_p == IPPROTO_UDP)
lnk = FindUdpTcpIn(la, ip->ip_dst, ip->ip_src,
ud->uh_dport, ud->uh_sport,
IPPROTO_UDP, 0);
else if (ip->ip_p == IPPROTO_TCP)
lnk = FindUdpTcpIn(la, ip->ip_dst, ip->ip_src,
tc->th_dport, tc->th_sport,
IPPROTO_TCP, 0);
else if (ip->ip_p == IPPROTO_ICMP) {
if (ic2->icmp_type == ICMP_ECHO || ic2->icmp_type == ICMP_TSTAMP)
lnk = FindIcmpIn(la, ip->ip_dst, ip->ip_src, ic2->icmp_id, 0);
else
lnk = NULL;
} else
lnk = NULL;
if (lnk != NULL) {
if (ip->ip_p == IPPROTO_UDP || ip->ip_p == IPPROTO_TCP) {
int accumulate, accumulate2;
struct in_addr original_address;
u_short original_port;
original_address = GetOriginalAddress(lnk);
original_port = GetOriginalPort(lnk);
/* Adjust ICMP checksum */
accumulate = twowords(&ip->ip_src);
accumulate -= twowords(&original_address);
accumulate += ud->uh_sport;
accumulate -= original_port;
accumulate2 = accumulate;
accumulate2 += ip->ip_sum;
ADJUST_CHECKSUM(accumulate, ip->ip_sum);
accumulate2 -= ip->ip_sum;
ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum);
/* Un-alias address in IP header */
DifferentialChecksum(&pip->ip_sum,
&original_address, &pip->ip_dst, 2);
pip->ip_dst = original_address;
/* Un-alias address and port number of original IP packet
fragment contained in ICMP data section */
ip->ip_src = original_address;
ud->uh_sport = original_port;
} else if (ip->ip_p == IPPROTO_ICMP) {
int accumulate, accumulate2;
struct in_addr original_address;
u_short original_id;
original_address = GetOriginalAddress(lnk);
original_id = GetOriginalPort(lnk);
/* Adjust ICMP checksum */
accumulate = twowords(&ip->ip_src);
accumulate -= twowords(&original_address);
accumulate += ic2->icmp_id;
accumulate -= original_id;
accumulate2 = accumulate;
accumulate2 += ip->ip_sum;
ADJUST_CHECKSUM(accumulate, ip->ip_sum);
accumulate2 -= ip->ip_sum;
ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum);
/* Un-alias address in IP header */
DifferentialChecksum(&pip->ip_sum,
&original_address, &pip->ip_dst, 2);
pip->ip_dst = original_address;
/* Un-alias address of original IP packet and sequence number of
embedded ICMP datagram */
ip->ip_src = original_address;
ic2->icmp_id = original_id;
}
return (PKT_ALIAS_OK);
}
return (PKT_ALIAS_IGNORED);
}
int
LibAliasUnaliasOut(struct libalias *la, char *ptr, /* valid IP packet */
int maxpacketsize /* for error checking */
)
{
struct ip *pip;
struct icmp *ic;
struct udphdr *ud;
struct tcphdr *tc;
struct alias_link *lnk;
int iresult = PKT_ALIAS_IGNORED;
LIBALIAS_LOCK(la);
pip = (struct ip *)ptr;
/* Defense against mangled packets */
if (ntohs(pip->ip_len) > maxpacketsize
|| (pip->ip_hl << 2) > maxpacketsize)
goto getout;
ud = (struct udphdr *)ip_next(pip);
tc = (struct tcphdr *)ip_next(pip);
ic = (struct icmp *)ip_next(pip);
/* Find a link */
if (pip->ip_p == IPPROTO_UDP)
lnk = FindUdpTcpIn(la, pip->ip_dst, pip->ip_src,
ud->uh_dport, ud->uh_sport,
IPPROTO_UDP, 0);
else if (pip->ip_p == IPPROTO_TCP)
lnk = FindUdpTcpIn(la, pip->ip_dst, pip->ip_src,
tc->th_dport, tc->th_sport,
IPPROTO_TCP, 0);
else if (pip->ip_p == IPPROTO_ICMP)
lnk = FindIcmpIn(la, pip->ip_dst, pip->ip_src, ic->icmp_id, 0);
else
lnk = NULL;
/* Change it from an aliased packet to an unaliased packet */
if (lnk != NULL) {
if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP) {
int accumulate;
struct in_addr original_address;
u_short original_port;
original_address = GetOriginalAddress(lnk);
original_port = GetOriginalPort(lnk);
/* Adjust TCP/UDP checksum */
accumulate = twowords(&pip->ip_src);
accumulate -= twowords(&original_address);
if (pip->ip_p == IPPROTO_UDP) {
accumulate += ud->uh_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
} else {
accumulate += tc->th_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, tc->th_sum);
}
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
&original_address, &pip->ip_src, 2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
if (pip->ip_p == IPPROTO_UDP)
ud->uh_sport = original_port;
else
tc->th_sport = original_port;
iresult = PKT_ALIAS_OK;
} else if (pip->ip_p == IPPROTO_ICMP) {
int accumulate;
struct in_addr original_address;
u_short original_id;
original_address = GetOriginalAddress(lnk);
original_id = GetOriginalPort(lnk);
/* Adjust ICMP checksum */
accumulate = twowords(&pip->ip_src);
accumulate -= twowords(&original_address);
accumulate += ic->icmp_id;
accumulate -= original_id;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
&original_address, &pip->ip_src, 2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
ic->icmp_id = original_id;
iresult = PKT_ALIAS_OK;
}
}
getout:
LIBALIAS_UNLOCK(la);
return (iresult);
}
int
PacketUnaliasOut(char *ptr, /* valid IP packet */
int maxpacketsize /* for error checking */
)
{
struct ip *pip;
struct icmp *ic;
struct udphdr *ud;
struct tcphdr *tc;
struct alias_link *link;
int iresult = PKT_ALIAS_IGNORED;
pip = (struct ip *) ptr;
/* Defense against mangled packets */
if (ntohs(pip->ip_len) > maxpacketsize
|| (pip->ip_hl<<2) > maxpacketsize)
return(iresult);
ud = (struct udphdr *) ((char *) pip + (pip->ip_hl << 2));
tc = (struct tcphdr *) ud;
ic = (struct icmp *) ud;
/* Find a link */
if (pip->ip_p == IPPROTO_UDP)
link = FindUdpTcpIn(pip->ip_dst, pip->ip_src,
ud->uh_dport, ud->uh_sport,
IPPROTO_UDP, 0);
else if (pip->ip_p == IPPROTO_TCP)
link = FindUdpTcpIn(pip->ip_dst, pip->ip_src,
tc->th_dport, tc->th_sport,
IPPROTO_TCP, 0);
else if (pip->ip_p == IPPROTO_ICMP)
link = FindIcmpIn(pip->ip_dst, pip->ip_src, ic->icmp_id, 0);
else
link = NULL;
/* Change it from an aliased packet to an unaliased packet */
if (link != NULL)
{
if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP)
{
u_short *sptr;
int accumulate;
struct in_addr original_address;
u_short original_port;
original_address = GetOriginalAddress(link);
original_port = GetOriginalPort(link);
/* Adjust TCP/UDP checksum */
sptr = (u_short *) &(pip->ip_src);
accumulate = *sptr++;
accumulate += *sptr;
sptr = (u_short *) &original_address;
accumulate -= *sptr++;
accumulate -= *sptr;
if (pip->ip_p == IPPROTO_UDP) {
accumulate += ud->uh_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
} else {
accumulate += tc->th_sport;
accumulate -= original_port;
ADJUST_CHECKSUM(accumulate, tc->th_sum);
}
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &original_address,
(u_short *) &pip->ip_src,
2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
if (pip->ip_p == IPPROTO_UDP)
ud->uh_sport = original_port;
else
tc->th_sport = original_port;
iresult = PKT_ALIAS_OK;
} else if (pip->ip_p == IPPROTO_ICMP) {
u_short *sptr;
int accumulate;
struct in_addr original_address;
u_short original_id;
original_address = GetOriginalAddress(link);
original_id = GetOriginalPort(link);
/* Adjust ICMP checksum */
sptr = (u_short *) &(pip->ip_src);
accumulate = *sptr++;
accumulate += *sptr;
sptr = (u_short *) &original_address;
accumulate -= *sptr++;
accumulate -= *sptr;
accumulate += ic->icmp_id;
accumulate -= original_id;
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
/* Adjust IP checksum */
DifferentialChecksum(&pip->ip_sum,
(u_short *) &original_address,
(u_short *) &pip->ip_src,
2);
/* Un-alias source address and port number */
pip->ip_src = original_address;
ic->icmp_id = original_id;
iresult = PKT_ALIAS_OK;
}
}
return(iresult);
}