From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH] pktgen: fix transmission headers with frags=0 Date: Mon, 14 Mar 2011 14:56:17 +0100 Message-ID: <1300110977.3423.16.camel@edumazet-laptop> References: <4D7E167E.2090807@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org, Robert Olsson , Jens Laas , Voravit Tanyingyong To: Daniel Turull Return-path: Received: from mail-fx0-f46.google.com ([209.85.161.46]:51578 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752527Ab1CNN4V (ORCPT ); Mon, 14 Mar 2011 09:56:21 -0400 Received: by fxm17 with SMTP id 17so2911529fxm.19 for ; Mon, 14 Mar 2011 06:56:20 -0700 (PDT) In-Reply-To: <4D7E167E.2090807@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Le lundi 14 mars 2011 =C3=A0 14:22 +0100, Daniel Turull a =C3=A9crit : > The headers of pktgen were incorrectly added in a pktgen packet > without frags (frags=3D0). There was an offset in the pktgen headers. >=20 > The cause was in reusing the pgh variable as a return variable in skb= _put > when adding the payload to the skb. >=20 > A rename of the variable is done. >=20 > Signed-off-by: Daniel Turull > --- > The PKTGEN magic (be9b e955) now starts in the correct offset. > Before the patch, it was starting at the end of the packet (be9b) >=20 not exactly, but offseted +16 bytes (sizeof(struct pktgen_hdr)) > Capture from tcpdump: >=20 > before patch: > 14:57:37.854812 IP 10.0.0.2.discard > 10.254.254.84.discard: UDP, len= gth 18 > 0x0000: 001b 2157 ed84 001b 215d 01d0 0800 4500 > 0x0010: 002e 0004 0000 2011 8767 0a00 0002 0afe > 0x0020: fe54 0009 0009 001a 0000 0000 0000 b072 > 0x0030: 9102 00ea ffff 0010 0000 be9b >=20 > after patch: > 14:44:32.896048 IP 10.0.0.2.discard > 10.217.234.56.discard: UDP, len= gth 18 > 0x0000: 001b 2157 ed84 001b 215d 01d0 0800 4500 > 0x0010: 002e 0000 0000 2011 9bac 0a00 0002 0ad9 > 0x0020: ea38 0009 0009 001a 0000 be9b e955 0000 > 0x0030: 0001 4d7e 1b09 0005 5f23 af00 >=20 > --- > diff --git a/net/core/pktgen.c b/net/core/pktgen.c > index f0aec6c..5baa9d9 100644 > --- a/net/core/pktgen.c > +++ b/net/core/pktgen.c > @@ -2615,13 +2615,14 @@ static void pktgen_finalize_skb(struct pktgen= _dev *pkt_dev, struct sk_buff *skb, > { > struct timeval timestamp; > struct pktgen_hdr *pgh; > + void *data; > =20 > pgh =3D (struct pktgen_hdr *)skb_put(skb, sizeof(*pgh)); > datalen -=3D sizeof(*pgh); > =20 > if (pkt_dev->nfrags <=3D 0) { > - pgh =3D (struct pktgen_hdr *)skb_put(skb, datalen); > - memset(pgh + 1, 0, datalen); > + data =3D skb_put(skb, datalen); > + memset(data + 1, 0, datalen); > } else { > int frags =3D pkt_dev->nfrags; > int i, len; > -- Good catch ! Hmm this patch is not correct, why memset(data + 1, ...) ? Also, this patch is needed for net-next-2.6 only (bug introduced by commit 26ad787962ef84677a48c560 (pktgen: speedup fragmented skbs) I would avoid the "void *data;" declaration and just use following : diff --git a/net/core/pktgen.c b/net/core/pktgen.c index f0aec6c..f727c83 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -2620,7 +2620,7 @@ static void pktgen_finalize_skb(struct pktgen_dev= *pkt_dev, struct sk_buff *skb, datalen -=3D sizeof(*pgh); =20 if (pkt_dev->nfrags <=3D 0) { - pgh =3D (struct pktgen_hdr *)skb_put(skb, datalen); + skb_put(skb, datalen); memset(pgh + 1, 0, datalen); } else { int frags =3D pkt_dev->nfrags; or even : memset(skb_put(skb, datalen), 0, datalen);