Hide the interface name in the sin_zero section of the sockaddr_in

passed to the user process for incoming packets. When the sockaddr_in
is passed back to the divert socket later, use thi sas the primary
interface lookup and only revert to the IP address when the name fails.
This solves a long standing bug with divert sockets:
When two interfaces had the same address (P2P for example) the interface
"assigned" to the reinjected packet was sometimes incorect.
Probably we should define a "sockaddr_div" to officially hold this
extended information in teh same manner as sockaddr_dl.

1 files changed, 11 insertions, 3 deletions

diff --git a/share/man/man4/divert.4 b/share/man/man4/divert.4
index b9aa0fb..522946c 100644
--- a/share/man/man4/divert.4
+++ b/share/man/man4/divert.4
@@ -1,4 +1,4 @@
-.\"	$Id: divert.4,v 1.9 1997/11/08 01:02:08 brian Exp $
+.\"	$Id: divert.4,v 1.10 1998/03/12 07:30:16 charnier Exp $
 .\"
 .Dd June 18, 1996
 .Dt DIVERT 4
@@ -47,7 +47,9 @@ the divert port and the IP address set to the (first) address of
 the interface on which the packet was received (if the packet
 was incoming) or
 .Dv INADDR_ANY
-(if the packet was outgoing).
+(if the packet was outgoing). In the case of an incoming packet the interface
+name will also be placed in the 8 bytes following the address,
+(assuming it fits).
 .Sh WRITING PACKETS
 Writing to a divert socket is similar to writing to a raw IP socket;
 the packet is injected ``as is'' into the normal kernel IP packet
@@ -66,7 +68,13 @@ for a non-local address.  Otherwise, the packet is assumed to be
 incoming and full packet routing is done.
 .Pp
 In the latter case, the
-IP address specified must match the address of some local interface.
+IP address specified must match the address of some local interface,
+or an interface name
+must be found after the IP address. If an interface name is found,
+that interface will be used and the value of the IP address will be
+ignored (other than the fact that it is not
+.Dv INADDR_ANY
+).
 This is to indicate on which interface the packet ``arrived.''
 .Pp
 Normally, packets read as incoming should be written as incoming;