From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fan Du Subject: Re: [PATCHv2 2/2] Don't compute checksum value for SCTP skb with, CHECKSUM_PARTIAL set Date: Sat, 12 Oct 2013 17:45:02 +0800 Message-ID: <52591A1E.7010705@windriver.com> References: <1381384296-1821-1-git-send-email-fan.du@windriver.com> <20131010131116.GA16147@hmsreliant.think-freely.org> <5257A3D6.3010002@windriver.com> <52580A68.9040502@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Neil Horman , , , To: Vlad Yasevich Return-path: Received: from mail.windriver.com ([147.11.1.11]:50100 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752526Ab3JLJqV (ORCPT ); Sat, 12 Oct 2013 05:46:21 -0400 In-Reply-To: <52580A68.9040502@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On 2013=E5=B9=B410=E6=9C=8811=E6=97=A5 22:25, Vlad Yasevich wrote: > On 10/11/2013 03:08 AM, Fan Du wrote: >> >> >> On 2013=E5=B9=B410=E6=9C=8810=E6=97=A5 21:11, Neil Horman wrote: >>> On Thu, Oct 10, 2013 at 01:51:36PM +0800, Fan Du wrote: >>>> igb/ixgbe have hardware sctp checksum support, when this feature i= s >>>> enabled >>>> and also IPsec is armed to protect sctp traffic, ugly things happe= ned as >>>> xfrm_output checks CHECKSUM_PARTIAL to do check sum operation(sum >>>> every thing >>>> up and pack the 16bits result in the checksum field). The result i= s fail >>>> establishment of sctp communication. >>>> >>> Shouldn't this be fixed in the xfrm code then? E.g. check the devic= e >>> features >>> for SCTP checksum offloading and and skip the checksum during xfrm >>> output if its >>> available? >>> >>> Or am I missing something? >>> Neil >>> >>> >> >> >> From cff25810910603ff991f0c56441d6de8dc33a822 Mon Sep 17 00:00:00 20= 01 >> From: Fan Du >> Date: Fri, 11 Oct 2013 14:31:57 +0800 >> Subject: [PATCH 2/2] Don't compute checksum value for SCTP skb with >> CHECKSUM_PARTIAL set >> MIME-Version: 1.0 >> Content-Type: text/plain; charset=3DUTF-8 >> Content-Transfer-Encoding: 8bit >> >> IPsec is not enabled in this scenario: >> >> SCTP skb set CHECKSUM_PARTIAL to indicate hardware is capable of doi= ng >> SCTP checksum(crc32-c) scoping the whole SCTP packet range. However = when >> such kind of skb is delivered through IPv4/v6 output handler, IPv4/v= 6 stack >> interpret CHECKSUM_PARTIAL by calling skb_checksum_help to compute 1= 6bits >> checksum value by summing everything up, the whole SCTP packet in so= ftware >> manner=EF=BC=81 After this skb reach NIC, after hardware doing its S= CTP checking >> business, a crc32-c value will overwrite the value IPv4/v6 stack com= puted >> before. >> >> This patch solves this by introducing skb_is_sctpv4/6 to optimize su= ch >> case. >> >> Signed-off-by: Fan Du >> --- >> v2: >> Rework this problem by introducing skb_is_scktv4/6 >> >> --- >> include/linux/ip.h | 5 +++++ >> include/linux/ipv6.h | 6 ++++++ >> include/linux/skbuff.h | 1 - >> net/core/skbuff.c | 1 + >> net/ipv4/ip_output.c | 4 +++- >> net/ipv6/ip6_output.c | 1 + >> net/xfrm/xfrm_output.c | 20 +++++++++++++++----- >> 7 files changed, 31 insertions(+), 7 deletions(-) >> >> diff --git a/include/linux/ip.h b/include/linux/ip.h >> index 492bc65..f556292 100644 >> --- a/include/linux/ip.h >> +++ b/include/linux/ip.h >> @@ -19,6 +19,7 @@ >> >> #include >> #include >> +#include >> >> static inline struct iphdr *ip_hdr(const struct sk_buff *skb) >> { >> @@ -34,4 +35,8 @@ static inline struct iphdr *ipip_hdr(const struct >> sk_buff *skb) >> { >> return (struct iphdr *)skb_transport_header(skb); >> } >> +static inline int skb_is_sctpv4(const struct sk_buff *skb) >> +{ >> + return ip_hdr(skb)->protocol =3D=3D IPPROTO_SCTP; >> +} >> #endif /* _LINUX_IP_H */ >> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h >> index 28ea384..6e17c04 100644 >> --- a/include/linux/ipv6.h >> +++ b/include/linux/ipv6.h >> @@ -2,6 +2,7 @@ >> #define _IPV6_H >> >> #include >> +#include >> >> #define ipv6_optlen(p) (((p)->hdrlen+1) << 3) >> /* >> @@ -387,4 +388,9 @@ static inline struct raw6_sock *raw6_sk(const st= ruct >> sock *sk) >> ((__sk)->sk_bound_dev_if =3D=3D (__dif))) && \ >> net_eq(sock_net(__sk), (__net))) >> >> +static inline int skb_is_sctpv6(const struct sk_buff *skb) >> +{ >> + return ipv6_hdr(skb)->nexthdr =3D=3D IPPROTO_SCTP; >> +} >> + >> #endif /* _IPV6_H */ >> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h >> index 2ddb48d..b36d0cc 100644 >> --- a/include/linux/skbuff.h >> +++ b/include/linux/skbuff.h >> @@ -2393,7 +2393,6 @@ extern void skb_split(struct sk_buff *skb, >> extern int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, >> int shiftlen); >> extern void skb_scrub_packet(struct sk_buff *skb, bool xnet); >> - >> extern struct sk_buff *skb_segment(struct sk_buff *skb, >> netdev_features_t features); >> >> diff --git a/net/core/skbuff.c b/net/core/skbuff.c >> index d81cff1..54d6172 100644 >> --- a/net/core/skbuff.c >> +++ b/net/core/skbuff.c >> @@ -3526,3 +3526,4 @@ void skb_scrub_packet(struct sk_buff *skb, boo= l xnet) >> nf_reset_trace(skb); >> } >> EXPORT_SYMBOL_GPL(skb_scrub_packet); >> + >> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c >> index a04d872..8676b2c 100644 >> --- a/net/ipv4/ip_output.c >> +++ b/net/ipv4/ip_output.c >> @@ -587,7 +587,9 @@ slow_path_clean: >> >> slow_path: >> /* for offloaded checksums cleanup checksum before fragmentation */ >> - if ((skb->ip_summed =3D=3D CHECKSUM_PARTIAL) && skb_checksum_help(= skb)) >> + if ((skb->ip_summed =3D=3D CHECKSUM_PARTIAL) && >> + !skb_is_sctpv4(skb) && >> + skb_checksum_help(skb)) >> goto fail; >> iph =3D ip_hdr(skb); >> >> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c >> index 3a692d5..9b27d95 100644 >> --- a/net/ipv6/ip6_output.c >> +++ b/net/ipv6/ip6_output.c >> @@ -671,6 +671,7 @@ slow_path_clean: >> >> slow_path: >> if ((skb->ip_summed =3D=3D CHECKSUM_PARTIAL) && >> + !skb_is_sctpv6(skb) && >> skb_checksum_help(skb)) >> goto fail; >> > > No, this isn't right. This is a case where IP fragmentation is > required, and the above code will cause SCTP checksum to not be > computed. Ok, I got my ball, ten bucks bet this correct ;) IPv4: after skb reach fragmentation part, CHECKSUM_PARTIAL denotes L4 layer protocol need to be checksummed, then IPv4 checksum is recomputed for each fragmented IPv4 packet. IPv6: Here IPv6 doesn't need checksum for its header, again CHECKSUM_PARTIAL denotes L4 layer protocol need to be checksummed. So all in all, this is the right place to distinguish SCTP skb out, and skip checksum operation as hw does it thereafter. Q.E.D. > Looks like SCTP needs to compute the checksum in the case where > skb will be fragmented. > > An alternative, that will also allow us to get rid of patch 1 > in the serices is to have a checksum handler offload function > that can be used to compute checksum in this case. > > -vlad > >> diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c >> index 3bb2cdc..ddef94a 100644 >> --- a/net/xfrm/xfrm_output.c >> +++ b/net/xfrm/xfrm_output.c >> @@ -180,6 +180,14 @@ static int xfrm_output_gso(struct sk_buff *skb) >> return 0; >> } >> >> +static int skb_is_sctp(const struct sk_buff *skb) >> +{ >> + if (skb->protocol =3D=3D __constant_htons(ETH_P_IP)) >> + return skb_is_sctpv4(skb); >> + else >> + return skb_is_sctpv6(skb); >> +} >> + >> int xfrm_output(struct sk_buff *skb) >> { >> struct net *net =3D dev_net(skb_dst(skb)->dev); >> @@ -189,11 +197,13 @@ int xfrm_output(struct sk_buff *skb) >> return xfrm_output_gso(skb); >> >> if (skb->ip_summed =3D=3D CHECKSUM_PARTIAL) { >> - err =3D skb_checksum_help(skb); >> - if (err) { >> - XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR); >> - kfree_skb(skb); >> - return err; >> + if (!skb_is_sctp(skb)) { >> + err =3D skb_checksum_help(skb); >> + if (err) { >> + XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR); >> + kfree_skb(skb); >> + return err; >> + } >> } >> } >> > > --=20 =E6=B5=AE=E6=B2=89=E9=9A=8F=E6=B5=AA=E5=8F=AA=E8=AE=B0=E4=BB=8A=E6=9C=9D= =E7=AC=91 --fan