Don't get caught in an infinite recursion when PKT_ALIAS_REVERSE

is set.
Document PKT_ALIAS_REVERSE.

Pointed out by:	Jonathan Hanna <jh@cr1003333-a.crdva1.bc.home.com>
PR:		12304

2 files changed, 18 insertions, 5 deletions

diff --git a/sys/netinet/libalias/alias.c b/sys/netinet/libalias/alias.c
index 10e0ccc..8b18a73 100644
--- a/sys/netinet/libalias/alias.c
+++ b/sys/netinet/libalias/alias.c
@@ -1174,8 +1174,12 @@ PacketAliasIn(char *ptr, int maxpacketsize)
     struct ip *pip;
     int iresult;
 
-    if (packetAliasMode & PKT_ALIAS_REVERSE)
-        return PacketAliasOut(ptr, maxpacketsize);
+    if (packetAliasMode & PKT_ALIAS_REVERSE) {
+        packetAliasMode &= ~PKT_ALIAS_REVERSE;
+        iresult = PacketAliasOut(ptr, maxpacketsize);
+        packetAliasMode |= PKT_ALIAS_REVERSE;
+        return iresult;
+    }
 
     HouseKeeping();
     ClearCheckNewLink();
@@ -1256,8 +1260,12 @@ PacketAliasOut(char *ptr,           /* valid IP packet */
     struct in_addr addr_save;
     struct ip *pip;
 
-    if (packetAliasMode & PKT_ALIAS_REVERSE)
-        return PacketAliasIn(ptr, maxpacketsize);
+    if (packetAliasMode & PKT_ALIAS_REVERSE) {
+        packetAliasMode &= ~PKT_ALIAS_REVERSE;
+        iresult = PacketAliasIn(ptr, maxpacketsize);
+        packetAliasMode |= PKT_ALIAS_REVERSE;
+        return iresult;
+    }
 
     HouseKeeping();
     ClearCheckNewLink();
diff --git a/sys/netinet/libalias/libalias.3 b/sys/netinet/libalias/libalias.3
index fa6cad7..8e38d91 100644
--- a/sys/netinet/libalias/libalias.3
+++ b/sys/netinet/libalias/libalias.3
@@ -247,7 +247,7 @@ If this mode bit is not set, it the link table
 will never be reset in the event of an
 address change.
 .It PKT_ALIAS_PUNCH_FW.
-This option make libalias `punch holes' in an
+This option makes libalias `punch holes' in an
 ipfw based firewall for FTP/IRC DCC connections.
 The holes punched are bound by from/to IP address
 and port; it will not be possible to use a hole
@@ -259,6 +259,11 @@ clear the entire ipfw range allocated for holes.
 This will also happen on the initial call to
 PacketAliasSetFWBase().  This call must happen
 prior to setting this flag.
+.It PKT_ALIAS_REVERSE.
+This option makes libalias reverse the way it
+handles incoming and outgoing packets, allowing
+it to be fed data that passes through the internal
+interface rather than the external one.
 
 .El