From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ananyev, Konstantin" Subject: Re: [PATCH v3 2/5] gso: add TCP/IPv4 GSO support Date: Wed, 13 Sep 2017 09:38:23 +0000 Message-ID: <2601191342CEEE43887BDE71AB9772584F24A622@irsmsx105.ger.corp.intel.com> References: <1504598270-60080-1-git-send-email-jiayu.hu@intel.com> <1505184211-36728-1-git-send-email-jiayu.hu@intel.com> <1505184211-36728-3-git-send-email-jiayu.hu@intel.com> <2601191342CEEE43887BDE71AB9772584F249E8E@irsmsx105.ger.corp.intel.com> <20170913024801.GB44293@dpdk15.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: "dev@dpdk.org" , "Kavanagh, Mark B" , "Tan, Jianfeng" To: "Hu, Jiayu" Return-path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id 57655199B5 for ; Wed, 13 Sep 2017 11:38:26 +0200 (CEST) In-Reply-To: <20170913024801.GB44293@dpdk15.sh.intel.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > > > + > > > +int > > > +gso_tcp4_segment(struct rte_mbuf *pkt, > > > + uint16_t gso_size, > > > + uint8_t ipid_delta, > > > + struct rte_mempool *direct_pool, > > > + struct rte_mempool *indirect_pool, > > > + struct rte_mbuf **pkts_out, > > > + uint16_t nb_pkts_out) > > > +{ > > > + struct ipv4_hdr *ipv4_hdr; > > > + uint16_t tcp_dl; > > > + uint16_t pyld_unit_size; > > > + uint16_t hdr_offset; > > > + int ret =3D 1; > > > + > > > + ipv4_hdr =3D (struct ipv4_hdr *)(rte_pktmbuf_mtod(pkt, char *) + > > > + pkt->l2_len); > > > + /* Don't process the fragmented packet */ > > > + if (unlikely((ipv4_hdr->fragment_offset & rte_cpu_to_be_16( > > > + IPV4_HDR_DF_MASK)) =3D=3D 0)) { > > > > > > It is not a check for fragmented packet - it is a check that fragmentat= ion is allowed for that packet. > > Should be IPV4_HDR_DF_MASK - 1, I think. DF bit doesn't indicate is packet fragmented or not. It forbids to fragment packet any further. To check is packet already fragmented or not, you have to check MF bit and = frag_offset. Both have to be zero for un-fragmented packets. >=20 > IMO, IPV4_HDR_DF_MASK whose value is (1 << 14) is used to get DF bit. It'= s a > little-endian value. But ipv4_hdr->fragment_offset is big-endian order. > So the value of DF bit should be "ipv4_hdr->fragment_offset & rte_cpu_to_= be_16( > IPV4_HDR_DF_MASK)". If this value is 0, the input packet is fragmented. >=20 > > > > > + pkts_out[0] =3D pkt; > > > + return ret; > > > + } > > > + > > > + tcp_dl =3D rte_be_to_cpu_16(ipv4_hdr->total_length) - pkt->l3_len - > > > + pkt->l4_len; > > > > Why not use pkt->pkt_len - pkt->l2_len -pkt_l3_len - pkt_l4_len? >=20 > Yes, we can use pkt->pkt_len - pkt->l2_len -pkt_l3_len - pkt_l4_len here. >=20 > > > > > + /* Don't process the packet without data */ > > > + if (unlikely(tcp_dl =3D=3D 0)) { > > > + pkts_out[0] =3D pkt; > > > + return ret; > > > + } > > > + > > > + hdr_offset =3D pkt->l2_len + pkt->l3_len + pkt->l4_len; > > > + pyld_unit_size =3D gso_size - hdr_offset - ETHER_CRC_LEN; > > > > Hmm, why do we need to count CRC_LEN here? >=20 > Yes, we shouldn't count ETHER_CRC_LEN here. Its length should be > included in gso_size. Why? What is the point to account crc len into this computation? Why not just assume that gso_size is already a max_frame_size - crc_len As I remember, when we RX packet crc bytes will be already stripped, when user populates the packet, he doesn't care about crc bytes too.=20 Konstantin