From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f41.google.com (mail-wg0-f41.google.com [74.125.82.41]) by dpdk.org (Postfix) with ESMTP id 8AA0AC324 for ; Fri, 22 May 2015 15:34:40 +0200 (CEST) Received: by wgez8 with SMTP id z8so18149592wge.0 for ; Fri, 22 May 2015 06:34:40 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-type :content-disposition:in-reply-to; bh=dU9L/jI+JhmEsPiPWjU3rvD7kJa9XtuUGpZDBOhdxgQ=; b=Ymm/LKIsnjIyscjltiD0T4nr/QK/eHEuxzmiTGPztq7CcFocnFpxM5zouE4Joni6V5 lPRNcLb63M8J7V91h0FpFs42wa+J3oTsImvbLDwcF3zpsn9M/fSYi2iYuIuMExLo6Oh7 BNOg+ZHZAlLv9BZZjaRr28l4Hj8Nb6X8bI+y85zJgfKuroHXDJuag5asRyj+95Iq3ipg jxW3mnqzqatYOAffcTPqWCIB/Ce2zX8AjYpI4lcCCJBttkweYaJHobEdKQzZJp7nBL9Z iD1ui7Yex6vbkcYkHavrQTOIqF/SN+/P0Yvi13KQNvPXL3VsQR3jl0UeZjudgvLqiFRz c3MA== X-Gm-Message-State: ALoCoQmFTxnKgP4sL9EnImB+VPZv5IIpQFztZkLIThiPuvgo9w6Rv6/rxWeC2i6jZvmn7LL8i+OU X-Received: by 10.180.212.3 with SMTP id ng3mr7506462wic.92.1432301680276; Fri, 22 May 2015 06:34:40 -0700 (PDT) Received: from 6wind.com (guy78-3-82-239-227-177.fbx.proxad.net. [82.239.227.177]) by mx.google.com with ESMTPSA id d14sm3192070wjn.30.2015.05.22.06.34.38 (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 22 May 2015 06:34:39 -0700 (PDT) Date: Fri, 22 May 2015 15:34:34 +0200 From: Adrien Mazarguil To: Olivier MATZ Message-ID: <20150522133434.GG26795@6wind.com> Mail-Followup-To: Olivier MATZ , dev@dpdk.org References: <1432292852-15701-1-git-send-email-adrien.mazarguil@6wind.com> <1432292852-15701-2-git-send-email-adrien.mazarguil@6wind.com> <555F2420.8010200@6wind.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <555F2420.8010200@6wind.com> Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [PATCH 2/2] app/testpmd: compute checksum in icmpecho replies X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 22 May 2015 13:34:40 -0000 On Fri, May 22, 2015 at 02:42:08PM +0200, Olivier MATZ wrote: > Hi Adrien, Hi Olivier, > On 05/22/2015 01:07 PM, Adrien Mazarguil wrote: > > ICMP echo replies with invalid checksums may be dropped by network nodes or > > ignored by the ping utility. > > > > Signed-off-by: Adrien Mazarguil > > Acked-by: Ivan Boule > > --- > > app/test-pmd/icmpecho.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/app/test-pmd/icmpecho.c b/app/test-pmd/icmpecho.c > > index c5933f4..c278baf 100644 > > --- a/app/test-pmd/icmpecho.c > > +++ b/app/test-pmd/icmpecho.c > > @@ -445,7 +445,8 @@ reply_to_icmp_echo_rqsts(struct fwd_stream *fs) > > * - switch IPv4 source and destinations addresses, > > * - set IP_ICMP_ECHO_REPLY in ICMP header. > > * No need to re-compute the IP header checksum. > > - * Reset ICMP checksum. > > + * ICMP checksum is computed by assuming it is valid in the > > + * echo request and not verified. > > */ > > ether_addr_copy(ð_h->s_addr, ð_addr); > > ether_addr_copy(ð_h->d_addr, ð_h->s_addr); > > @@ -454,7 +455,7 @@ reply_to_icmp_echo_rqsts(struct fwd_stream *fs) > > ip_h->src_addr = ip_h->dst_addr; > > ip_h->dst_addr = ip_addr; > > icmp_h->icmp_type = IP_ICMP_ECHO_REPLY; > > - icmp_h->icmp_cksum = 0; > > + icmp_h->icmp_cksum += htons(IP_ICMP_ECHO_REQUEST << 8); > > > I don't think this checksum calculation method is always correct. > > Example of a working case: > > >>> p=Ether(str(Ether()/IP()/ICMP(seq=0))) > >>> p > version=4L ihl=5L tos=0x0 len=28 id=1 flags= frag=0L ttl=64 proto=icmp > chksum=0x7cde src=127.0.0.1 dst=127.0.0.1 options=[] | type=echo-request code=0 chksum=0xf7ff id=0x0 seq=0x0 |>>> > >>> del(p[ICMP].chksum) > >>> p[ICMP].type = 0 > >>> p=Ether(str(p)) > >>> p > version=4L ihl=5L tos=0x0 len=28 id=1 flags= frag=0L ttl=64 proto=icmp > chksum=0x7cde src=127.0.0.1 dst=127.0.0.1 options=[] | type=echo-reply code=0 chksum=0xffff id=0x0 seq=0x0 |>>> > > We have 0xffff - 0xf7ff = 0x0800 > > > Example of a non-working case: > > >>> p=Ether(str(Ether()/IP()/ICMP(seq=0xf800))) > >>> p > version=4L ihl=5L tos=0x0 len=28 id=1 flags= frag=0L ttl=64 proto=icmp > chksum=0x7cde src=127.0.0.1 dst=127.0.0.1 options=[] | type=echo-request code=0 chksum=0xfffe id=0x0 seq=0xf800 |>>> > >>> del(p[ICMP].chksum) > >>> p[ICMP].type = 0 > >>> p=Ether(str(p)) > >>> p > version=4L ihl=5L tos=0x0 len=28 id=1 flags= frag=0L ttl=64 proto=icmp > chksum=0x7cde src=127.0.0.1 dst=127.0.0.1 options=[] | type=echo-reply code=0 chksum=0x7ff id=0x0 seq=0xf800 |>>> > > Here, 0x7ff - 0xfffe != 0x08000 > > > A correct solution (not tested) would be something like: > > uint32_t cksum; > cksum = (~(icmp_h->icmp_cksum)) & 0xffff; > cksum += (~htons(IP_ICMP_ECHO_REQUEST << 8)) & 0xffff; > cksum += (htons(IP_ICMP_ECHO_REPLY << 8)) & 0xffff; > cksum = (cksum & 0xffff) + (cksum >> 16); > cksum = (cksum & 0xffff) + (cksum >> 16); > icmp_h->icmp_cksum = (~cksum) & 0xffff; You're right, my patch is taking too many shortcuts. I'll submit a new patch with your suggestion. Regards, -- Adrien Mazarguil 6WIND