From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Sommerfeld Subject: [PATCH] Constrain UFO fragment sizes to multiples of 8 bytes Date: Tue, 19 Jul 2011 18:22:33 -0700 Message-ID: <1311124953-32159-1-git-send-email-wsommerfeld@google.com> Cc: netdev@vger.kernel.org, Tom Herbert , =?UTF-8?q?Maciej=20=C5=BBenczykowski?= , Bill Sommerfeld To: "David S. Miller" Return-path: Received: from smtp-out.google.com ([74.125.121.67]:43097 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752595Ab1GTBXB (ORCPT ); Tue, 19 Jul 2011 21:23:01 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Because the ip fragment offset field counts 8-byte chunks, ip fragments other than the last must contain a multiple of 8 bytes of payload. ip_ufo_append_data wasn't respecting this constraint and, depending on the MTU and ip option sizes, could create malformed non-final fragments. Google-Bug-Id: 5009328 Signed-off-by: Bill Sommerfeld --- Note to reviewers: The first two hunks simply rename the "mtu" parameter to "maxfraglen"; the real change is in the third hunk. maxfraglen (the size of the largest non-final fragment which fits inside mtu) is already computed for the non-UFO fragmentation path. We saw this problem in a 2.6.34-based kernel with a bond device that had UFO enabled (as a result of changeset d9f5950f90292f7c); 1742f183fc218798 rewrote netdev_increment_features to no longer force on UFO. The MTU on this bond device was set to 1470; fragmented datagrams were mangled, causing the receiver to get errors of the form: [506259.362640] UDP: short packet: From x.x.x.x:nnnn 1471/1469 to y.y.y.y:nnnn net/ipv4/ip_output.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index be27e60..ccaaa85 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -734,7 +734,7 @@ static inline int ip_ufo_append_data(struct sock *sk, int getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb), void *from, int length, int hh_len, int fragheaderlen, - int transhdrlen, int mtu, unsigned int flags) + int transhdrlen, int maxfraglen, unsigned int flags) { struct sk_buff *skb; int err; @@ -767,7 +767,7 @@ static inline int ip_ufo_append_data(struct sock *sk, skb->csum = 0; /* specify the length of each IP datagram fragment */ - skb_shinfo(skb)->gso_size = mtu - fragheaderlen; + skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen; skb_shinfo(skb)->gso_type = SKB_GSO_UDP; __skb_queue_tail(queue, skb); } @@ -831,7 +831,7 @@ static int __ip_append_data(struct sock *sk, (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) { err = ip_ufo_append_data(sk, queue, getfrag, from, length, hh_len, fragheaderlen, transhdrlen, - mtu, flags); + maxfraglen, flags); if (err) goto error; return 0; -- 1.7.3.1