From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42111) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eFWtI-0005LG-0r for qemu-devel@nongnu.org; Thu, 16 Nov 2017 22:00:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eFWtE-0002m0-2T for qemu-devel@nongnu.org; Thu, 16 Nov 2017 22:00:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55460) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eFWtD-0002kj-Iv for qemu-devel@nongnu.org; Thu, 16 Nov 2017 22:00:23 -0500 References: <1510841166-40615-1-git-send-email-eswierk@skyportsystems.com> From: Jason Wang Message-ID: <760b9a11-1493-3ee4-8fd0-39897e5e98e7@redhat.com> Date: Fri, 17 Nov 2017 11:00:16 +0800 MIME-Version: 1.0 In-Reply-To: <1510841166-40615-1-git-send-email-eswierk@skyportsystems.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v3 REPOST] net: Transmit zero UDP checksum as 0xFFFF List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Ed Swierk , "Daniel P . Berrange" , Stefan Hajnoczi , Dmitry Fleytman Cc: qemu-devel@nongnu.org On 2017=E5=B9=B411=E6=9C=8816=E6=97=A5 22:06, Ed Swierk wrote: > The checksum algorithm used by IPv4, TCP and UDP allows a zero value > to be represented by either 0x0000 and 0xFFFF. But per RFC 768, a zero > UDP checksum must be transmitted as 0xFFFF because 0x0000 is a special > value meaning no checksum. > > Substitute 0xFFFF whenever a checksum is computed as zero when > modifying a UDP datagram header. Doing this on IPv4 and TCP checksums > is unnecessary but legal. Add a wrapper for net_checksum_finish() that > makes the substitution. > > (We can't just change net_checksum_finish(), as that function is also > used by receivers to verify checksums, and in that case the expected > value is always 0x0000.) > > Signed-off-by: Ed Swierk > --- > v3: > > (Reposted to fix patch format) > > Leave net_tx_pkt_update_ip_checksums() alone since it's only computing > a partial sum of the IP pseudo-header. > > Rename wrapper to net_checksum_finish_nozero() for clarity. > > v2: > > Add a wrapper net_checksum_finish_hdr() rather than duplicating the > logic at every caller. > --- > hw/net/e1000.c | 2 +- > hw/net/net_rx_pkt.c | 2 +- > hw/net/net_tx_pkt.c | 2 +- > hw/net/vmxnet3.c | 3 ++- > include/net/checksum.h | 6 ++++++ > 5 files changed, 11 insertions(+), 4 deletions(-) > > diff --git a/hw/net/e1000.c b/hw/net/e1000.c > index 72a92be..804ec08 100644 > --- a/hw/net/e1000.c > +++ b/hw/net/e1000.c > @@ -506,7 +506,7 @@ putsum(uint8_t *data, uint32_t n, uint32_t sloc, ui= nt32_t css, uint32_t cse) > n =3D cse + 1; > if (sloc < n-1) { > sum =3D net_checksum_add(n-css, data+css); > - stw_be_p(data + sloc, net_checksum_finish(sum)); > + stw_be_p(data + sloc, net_checksum_finish_nozero(sum)); > } > } > =20 > diff --git a/hw/net/net_rx_pkt.c b/hw/net/net_rx_pkt.c > index cef1c2e..98a5030 100644 > --- a/hw/net/net_rx_pkt.c > +++ b/hw/net/net_rx_pkt.c > @@ -518,7 +518,7 @@ _net_rx_pkt_calc_l4_csum(struct NetRxPkt *pkt) > cntr +=3D net_checksum_add_iov(pkt->vec, pkt->vec_len, > pkt->l4hdr_off, csl, cso); > =20 > - csum =3D net_checksum_finish(cntr); > + csum =3D net_checksum_finish_nozero(cntr); > =20 > trace_net_rx_pkt_l4_csum_calc_csum(pkt->l4hdr_off, csl, cntr, csu= m); > =20 > diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c > index 20b2549..e29c881 100644 > --- a/hw/net/net_tx_pkt.c > +++ b/hw/net/net_tx_pkt.c > @@ -486,7 +486,7 @@ static void net_tx_pkt_do_sw_csum(struct NetTxPkt *= pkt) > net_checksum_add_iov(iov, iov_len, pkt->virt_hdr.csum_start, = csl, cso); > =20 > /* Put the checksum obtained into the packet */ > - csum =3D cpu_to_be16(net_checksum_finish(csum_cntr)); > + csum =3D cpu_to_be16(net_checksum_finish_nozero(csum_cntr)); > iov_from_buf(iov, iov_len, csum_offset, &csum, sizeof csum); > } > =20 > diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c > index 8c4bae5..cdc307d 100644 > --- a/hw/net/vmxnet3.c > +++ b/hw/net/vmxnet3.c > @@ -972,7 +972,8 @@ static void vmxnet3_rx_need_csum_calculate(struct N= etRxPkt *pkt, > data =3D (uint8_t *)pkt_data + vhdr->csum_start; > len =3D pkt_len - vhdr->csum_start; > /* Put the checksum obtained into the packet */ > - stw_be_p(data + vhdr->csum_offset, net_raw_checksum(data, len)); > + stw_be_p(data + vhdr->csum_offset, > + net_checksum_finish_nozero(net_checksum_add(len, data))); > =20 > vhdr->flags &=3D ~VIRTIO_NET_HDR_F_NEEDS_CSUM; > vhdr->flags |=3D VIRTIO_NET_HDR_F_DATA_VALID; > diff --git a/include/net/checksum.h b/include/net/checksum.h > index 7df472c..05a0d27 100644 > --- a/include/net/checksum.h > +++ b/include/net/checksum.h > @@ -34,6 +34,12 @@ net_checksum_add(int len, uint8_t *buf) > } > =20 > static inline uint16_t > +net_checksum_finish_nozero(uint32_t sum) > +{ > + return net_checksum_finish(sum) ?: 0xFFFF; > +} > + > +static inline uint16_t > net_raw_checksum(uint8_t *data, int length) > { > return net_checksum_finish(net_checksum_add(length, data)); Applied, thanks.