From e6d8b64b34aa8a9fe39609bc2db8a243b0331ceb Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 30 Oct 2013 11:50:52 +0100 Subject: net: sctp: fix and consolidate SCTP checksumming code This fixes an outstanding bug found through IPVS, where SCTP packets with skb->data_len > 0 (non-linearized) and empty frag_list, but data accumulated in frags[] member, are forwarded with incorrect checksum letting SCTP initial handshake fail on some systems. Linearizing each SCTP skb in IPVS to prevent that would not be a good solution as this leads to an additional and unnecessary performance penalty on the load-balancer itself for no good reason (as we actually only want to update the checksum, and can do that in a different/better way presented here). The actual problem is elsewhere, namely, that SCTP's checksumming in sctp_compute_cksum() does not take frags[] into account like skb_checksum() does. So while we are fixing this up, we better reuse the existing code that we have anyway in __skb_checksum() and use it for walking through the data doing checksumming. This will not only fix this issue, but also consolidates some SCTP code with core sk_buff code, bringing it closer together and removing respectively avoiding reimplementation of skb_checksum() for no good reason. As crc32c() can use hardware implementation within the crypto layer, we leave that intact (it wraps around / falls back to e.g. slice-by-8 algorithm in __crc32c_le() otherwise); plus use the __crc32c_le_combine() combinator for crc32c blocks. Also, we remove all other SCTP checksumming code, so that we only have to use sctp_compute_cksum() from now on; for doing that, we need to transform SCTP checkumming in output path slightly, and can leave the rest intact. Signed-off-by: Daniel Borkmann Signed-off-by: David S. Miller --- net/sctp/output.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) (limited to 'net/sctp/output.c') diff --git a/net/sctp/output.c b/net/sctp/output.c index 319137340d15..e650978daf27 100644 --- a/net/sctp/output.c +++ b/net/sctp/output.c @@ -390,7 +390,6 @@ int sctp_packet_transmit(struct sctp_packet *packet) __u8 has_data = 0; struct dst_entry *dst = tp->dst; unsigned char *auth = NULL; /* pointer to auth in skb data */ - __u32 cksum_buf_len = sizeof(struct sctphdr); pr_debug("%s: packet:%p\n", __func__, packet); @@ -493,7 +492,6 @@ int sctp_packet_transmit(struct sctp_packet *packet) if (chunk == packet->auth) auth = skb_tail_pointer(nskb); - cksum_buf_len += chunk->skb->len; memcpy(skb_put(nskb, chunk->skb->len), chunk->skb->data, chunk->skb->len); @@ -538,12 +536,7 @@ int sctp_packet_transmit(struct sctp_packet *packet) if (!sctp_checksum_disable) { if (!(dst->dev->features & NETIF_F_SCTP_CSUM) || (dst_xfrm(dst) != NULL) || packet->ipfragok) { - __u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len); - - /* 3) Put the resultant value into the checksum field in the - * common header, and leave the rest of the bits unchanged. - */ - sh->checksum = sctp_end_cksum(crc32); + sh->checksum = sctp_compute_cksum(nskb, 0); } else { /* no need to seed pseudo checksum for SCTP */ nskb->ip_summed = CHECKSUM_PARTIAL; -- cgit v1.2.3