SCTP: Fix chunk parameter processing bug

If an address family is not listed in "Supported Address Types" parameter(INIT Chunk),
but the packet is sent by that family, this address family should be considered as supported by peer. Otherwise, an error condition will occur. For instance, if kernel receives an IPV6 SCTP INIT chunk with "Support Address Types" parameter which indicates just supporting IPV4 Address family. Kernel will reply an IPV6 SCTP INIT ACK packet, but the source ipv6 address in ipv6 header will be vacant. This is not correct.

refer to RFC4460 as following:
IMPLEMENTATION NOTE: If an SCTP endpoint lists in the 'Supported Address Types' parameter either IPv4 or IPv6, but uses the other family for sending the packet containing the INIT chunk, or if it also lists addresses of the other family in the INIT chunk, then the address family that is not listed in the 'Supported Address Types' parameter SHOULD also be considered as supported by the receiver of the INIT chunk. The receiver of the INIT chunk SHOULD NOT respond with any kind of error indication.

Here is a fix to comply to RFC.

---
 net/sctp/sm_make_chunk.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

index e45be4e..ed5d413 100644
@@ -2375,6 +2375,14 @@ static int sctp_process_param(struct sctp_association *asoc,
 		asoc->peer.ipv4_address = 0;
 		asoc->peer.ipv6_address = 0;
 
+		/* Assume that peer supports the address family 
+		   by which it sends a packet.
+		*/
+		if (peer_addr->sa.sa_family == AF_INET6)
+			asoc->peer.ipv6_address = 1;
+		else if (peer_addr->sa.sa_family == AF_INET)
+			asoc->peer.ipv4_address = 1;
+
 		/* Cycle through address types; avoid divide by 0. */
 		sat = ntohs(param.p->length) - sizeof(sctp_paramhdr_t);
 		if (sat)

1.5.3


-- 
Regards
Gui Jianfeng

Thanks for catching this.
-vlad

From: Vlad Yasevich <[email protected]>
Date: Wed, 05 Mar 2008 08:53:45 -0500

I applied this after killing trailing whitespace errors and making the added comment conform to kernel coding standards.

Thanks.