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Implement UDP transparent proxy support.

Browse Source 
PR:		bin/54274
Submitted by:	Nicolai Petri <nicolai@petri.cc>
This commit is contained in:
Alexander Motin 2008-06-21 20:18:57 +00:00
parent c0ff67d57f
commit ea29dd9241
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=179920
1 changed files with 76 additions and 10 deletions
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86
sys/netinet/libalias/alias.c
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@ -271,7 +271,7 @@ static int ProtoAliasOut(struct libalias *la, struct in_addr *ip_src,
int create);
static int UdpAliasIn(struct libalias *, struct ip *);
static int UdpAliasOut(struct libalias *, struct ip *, int create);
static int UdpAliasOut(struct libalias *, struct ip *, int, int create);
static int TcpAliasIn(struct libalias *, struct ip *);
static int TcpAliasOut(struct libalias *, struct ip *, int, int create);
@ -717,19 +717,18 @@ UdpAliasIn(struct libalias *la, struct ip *pip)
struct alias_link *lnk;
LIBALIAS_LOCK_ASSERT(la);
/* Return if proxy-only mode is enabled */
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
return (PKT_ALIAS_OK);
ud = (struct udphdr *)ip_next(pip);
lnk = FindUdpTcpIn(la, pip->ip_src, pip->ip_dst,
ud->uh_sport, ud->uh_dport,
IPPROTO_UDP, 1);
IPPROTO_UDP, !(la->packetAliasMode & PKT_ALIAS_PROXY_ONLY));
if (lnk != 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;
int r = 0, error;
struct alias_data ad = {
@ -744,8 +743,10 @@ UdpAliasIn(struct libalias *la, struct ip *pip)
alias_address = GetAliasAddress(lnk);
original_address = GetOriginalAddress(lnk);
proxy_address = GetProxyAddress(lnk);
alias_port = ud->uh_dport;
ud->uh_dport = GetOriginalPort(lnk);
proxy_port = GetProxyPort(lnk);
/* Walk out chain. */
error = find_handler(IN, UDP, la, pip, &ad);
@ -757,8 +758,32 @@ UdpAliasIn(struct libalias *la, struct ip *pip)
accumulate -= ud->uh_dport;
accumulate += twowords(&alias_address);
accumulate -= twowords(&original_address);
/* If this is a proxy packet, modify checksum because of source change.*/
if (proxy_port != 0) {
accumulate += ud->uh_sport;
accumulate -= proxy_port;
}
if (proxy_address.s_addr != 0) {
accumulate += twowords(&pip->ip_src);
accumulate -= twowords(&proxy_address);
}
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
}
/* XXX: Could the two if's below be concatenated to one ? */
/* Restore source port and/or address in case of proxying*/
if (proxy_port != 0)
ud->uh_sport = proxy_port;
if (proxy_address.s_addr != 0) {
DifferentialChecksum(&pip->ip_sum,
&proxy_address, &pip->ip_src, 2);
pip->ip_src = proxy_address;
}
/* Restore original IP address */
DifferentialChecksum(&pip->ip_sum,
&original_address, &pip->ip_dst, 2);
@ -776,19 +801,50 @@ UdpAliasIn(struct libalias *la, struct ip *pip)
}
static int
UdpAliasOut(struct libalias *la, struct ip *pip, int create)
UdpAliasOut(struct libalias *la, struct ip *pip, int maxpacketsize, int create)
{
struct udphdr *ud;
struct alias_link *lnk;
struct in_addr dest_address;
struct in_addr proxy_server_address;
u_short dest_port;
u_short proxy_server_port;
int proxy_type;
int error;
LIBALIAS_LOCK_ASSERT(la);
/* Return if proxy-only mode is enabled */
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
/* Return if proxy-only mode is enabled and not proxyrule found.*/
ud = (struct udphdr *)ip_next(pip);
proxy_type = ProxyCheck(la, &proxy_server_address,
&proxy_server_port, pip->ip_src, pip->ip_dst,
ud->uh_dport, pip->ip_p);
if (proxy_type == 0 && (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY))
return (PKT_ALIAS_OK);
ud = (struct udphdr *)ip_next(pip);
/* If this is a transparent proxy, save original destination,
* then alter the destination and adjust checksums */
dest_port = ud->uh_dport;
dest_address = pip->ip_dst;
if (proxy_type != 0) {
int accumulate;
accumulate = twowords(&pip->ip_dst);
accumulate -= twowords(&proxy_server_address);
ADJUST_CHECKSUM(accumulate, pip->ip_sum);
if (ud->uh_sum != 0) {
accumulate = twowords(&pip->ip_dst);
accumulate -= twowords(&proxy_server_address);
accumulate += ud->uh_dport;
accumulate -= proxy_server_port;
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
}
pip->ip_dst = proxy_server_address;
ud->uh_dport = proxy_server_port;
}
lnk = FindUdpTcpOut(la, pip->ip_src, pip->ip_dst,
ud->uh_sport, ud->uh_dport,
IPPROTO_UDP, create);
@ -805,6 +861,16 @@ UdpAliasOut(struct libalias *la, struct ip *pip, int create)
.maxpktsize = 0
};
/* Save original destination address, if this is a proxy packet.
* Also modify packet to include destination encoding. This may
* change the size of IP header. */
if (proxy_type != 0) {
SetProxyPort(lnk, dest_port);
SetProxyAddress(lnk, dest_address);
ProxyModify(la, lnk, pip, maxpacketsize, proxy_type);
ud = (struct udphdr *)ip_next(pip);
}
alias_address = GetAliasAddress(lnk);
alias_port = GetAliasPort(lnk);
@ -1409,7 +1475,7 @@ LibAliasOutLocked(struct libalias *la, char *ptr, /* valid IP packet */
iresult = IcmpAliasOut(la, pip, create);
break;
case IPPROTO_UDP:
iresult = UdpAliasOut(la, pip, create);
iresult = UdpAliasOut(la, pip, maxpacketsize, create);
break;
case IPPROTO_TCP:
iresult = TcpAliasOut(la, pip, maxpacketsize, create);