From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: [PATCH net] Revert "ipv6: Allow for partial checksums on non-ufo packets" Date: Tue, 12 May 2015 14:05:40 -0400 Message-ID: <555240F4.4070406@gmail.com> References: <1770409.aMESoOv08f@h2o.as.studentenwerk.mhn.de> <1431002384.22756.0.camel@edumazet-glaptop2.roam.corp.google.com> <12346713.ZyFExCo3ux@h2o.as.studentenwerk.mhn.de> <2088438.42IY8hjjd5@h2o.as.studentenwerk.mhn.de> <1431122268.22756.41.camel@edumazet-glaptop2.roam.corp.google.com> <1431123765.22756.51.camel@edumazet-glaptop2.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev To: Eric Dumazet , Wolfgang Walter Return-path: Received: from mail-qg0-f48.google.com ([209.85.192.48]:36627 "EHLO mail-qg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932776AbbELSFn (ORCPT ); Tue, 12 May 2015 14:05:43 -0400 Received: by qgeb100 with SMTP id b100so8615365qge.3 for ; Tue, 12 May 2015 11:05:42 -0700 (PDT) In-Reply-To: <1431123765.22756.51.camel@edumazet-glaptop2.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: On 05/08/2015 06:22 PM, Eric Dumazet wrote: > From: Eric Dumazet > > Wolfgang Walter reported crashes using traceroute6, root caused to this > commit. > > UDP packets can be sent from RAW sockets. > > Note that the faulty commit addressed a non problem, as normal > UDP v6 packets use udp_v6_send_skb() which correctly setup > CHECKSUM_PARTIAL properly if device has the correct feature. Actually, they didn't. udp_v6_send_skb() uses ip_summed from the skb, which is populated by __ip6_append_data. That in turn always set it CHECKSUM_NONE. The code in question looks identically to that of __ip_append_data(). The problem is similar in both places. -vlad > > It seems not worth trying to 'fix' the raw path. > > Fixes: 32dce968dd98 ("ipv6: Allow for partial checksums on non-ufo packets") > Signed-off-by: Eric Dumazet > Reported-by: Wolfgang Walter > Cc: Vlad Yasevich > --- > net/ipv6/ip6_output.c | 11 +---------- > 1 file changed, 1 insertion(+), 10 deletions(-) > > diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c > index 7fde1f265c90..1fe5c687328e 100644 > --- a/net/ipv6/ip6_output.c > +++ b/net/ipv6/ip6_output.c > @@ -1218,7 +1218,6 @@ static int __ip6_append_data(struct sock *sk, > u32 tskey = 0; > struct rt6_info *rt = (struct rt6_info *)cork->dst; > struct ipv6_txoptions *opt = v6_cork->opt; > - int csummode = CHECKSUM_NONE; > > skb = skb_peek_tail(queue); > if (!skb) { > @@ -1275,14 +1274,6 @@ emsgsize: > tskey = sk->sk_tskey++; > } > > - /* If this is the first and only packet and device > - * supports checksum offloading, let's use it. > - */ > - if (!skb && sk->sk_protocol == IPPROTO_UDP && > - length + fragheaderlen < mtu && > - rt->dst.dev->features & NETIF_F_V6_CSUM && > - !exthdrlen) > - csummode = CHECKSUM_PARTIAL; > /* > * Let's try using as much space as possible. > * Use MTU if total length of the message fits into the MTU. > @@ -1396,7 +1387,7 @@ alloc_new_skb: > * Fill in the control structures > */ > skb->protocol = htons(ETH_P_IPV6); > - skb->ip_summed = csummode; > + skb->ip_summed = CHECKSUM_NONE; > skb->csum = 0; > /* reserve for fragmentation and ipsec header */ > skb_reserve(skb, hh_len + sizeof(struct frag_hdr) + > >