> -----Original Message----- > From: Ophir Munk [mailto:ophi...@mellanox.com] > Sent: Tuesday, April 24, 2018 10:44 AM > To: Hu, Jiayu <jiayu...@intel.com>; dev@dpdk.org; Ananyev, Konstantin > <konstantin.anan...@intel.com> > Cc: Thomas Monjalon <tho...@monjalon.net>; Olga Shern <ol...@mellanox.com>; > Pascal Mazon <pascal.ma...@6wind.com>; > sta...@dpdk.org > Subject: RE: [PATCH v1] gso: fix marking TCP checksum flag in TCP segments > > Hi Jiayu, > Please find comments inline > > > -----Original Message----- > > From: Hu, Jiayu [mailto:jiayu...@intel.com] > > Sent: Monday, April 23, 2018 7:14 AM > > To: Ophir Munk <ophi...@mellanox.com>; dev@dpdk.org; Ananyev, > > Konstantin <konstantin.anan...@intel.com> > > Cc: Thomas Monjalon <tho...@monjalon.net>; Olga Shern > > <ol...@mellanox.com>; Pascal Mazon <pascal.ma...@6wind.com>; > > sta...@dpdk.org > > Subject: RE: [PATCH v1] gso: fix marking TCP checksum flag in TCP segments > > > > Hi Ophir, > > > > In the GSO design, the GSO library doesn't care about checksums, which > > means it doesn't check if input packets have correct checksums, and it > > doesn't do any checksum related work for the output GSO segments. It > > depends on the callers to use HW or SW checksum calculation for output > > packets. This is why the GSO library doesn't set PKT_TX_TCP_CKSUM. So I > > don't think it's a bug. > > > > Can you please reconsider this design? I think the GSO library should imitate > the HW behavior where TCP segments checksum is > automatically calculated without explicitly requesting it. I am not saying > that GSO library itself should calculate the checksums - but at least > it should mark each segment as requiring this calculation.
But gso has no idea how this packet will be processed after it. Caller can choose to calculate L3/L4 cksum in SW or might be going to use HW offloads. In later case nothing stops the caller to update mbuf->ol_flags in a way he likes (TCP_CKSUM, IP_CKSUM, etc.). Konstantin > > > In my opinion, it's not a good idea to enable HW TCP checksum calculation > > silently, and without the aware of the caller. In fact, the caller always > > know it > > does SW TSO (i.e. GSO), instead of real HW TSO. > > This is not correct. Consider net_failsafe with 2 sub-devices: one is a HW > PCI device, the other one is a SW TAP device. Failsafe must work > transparently with these two sub-devices and the caller cannot tell if TSO is > done in SW or HW. > > > If the caller wants HW > > checksum calculation, it can add PKT_TX_TCP_CKSUM to ol_flags before or > > after calling the GSO library. > > > > FYI - TAP TSO patches were submitted to dpdk.org mailing list. These patches > use the GSO library. > https://dpdk.org/dev/patchwork/patch/38666/ > https://dpdk.org/dev/patchwork/patch/38667/ > > Running testpmd with TAP TSO is currently broken without the suggested > librte_gso patch. > Please note testpmd implementation (app/test-pmd/csumonly.c > b/app/test-pmd/csumonly.c) in case *both* TSO and TCP CKSUM are > configured: > > if (tso_segsz) > ol_flags |= PKT_TX_TCP_SEG; // *** if TSO is applicable - the packet > flags are only marked with PKT_TX_TCP_SEG and no > PKT_TX_TCP_CKSUM *** > else if (tx_offloads & DEV_TX_OFFLOAD_TCP_CKSUM) > ol_flags |= PKT_TX_TCP_CKSUM; // *** PKT_TX_TCP_CKSUM is marked > only if TSO is not applicable *** > else { > tcp_hdr->cksum = > get_udptcp_checksum(l3_hdr, tcp_hdr, > > In other words - testpmd does not set TCP_CKSUM along with TCP_SEG therefore > using testpmd with TAP/TSO will result in TCP segments > with 0 (incorrect) TCP checksums. > > In addition - please note the comments in lib/librte_mbuf/rte_mbuf.h which > specify that PKT_TX_TCP_SEG flag implies the > PKT_TX_TCP_CKSUM (hence it is not required to be explicitly set by the caller) > > /** > * TCP segmentation offload. To enable this offload feature for a > * packet to be transmitted on hardware supporting TSO: > * - set the PKT_TX_TCP_SEG flag in mbuf->ol_flags (this flag implies > * PKT_TX_TCP_CKSUM) > ... > > > Add Konstantin for more suggestions. > > > > Thanks, > > Jiayu > > > > > -----Original Message----- > > > From: Ophir Munk [mailto:ophi...@mellanox.com] > > > Sent: Sunday, April 22, 2018 10:21 PM > > > To: dev@dpdk.org; Hu, Jiayu <jiayu...@intel.com> > > > Cc: Thomas Monjalon <tho...@monjalon.net>; Olga Shern > > > <ol...@mellanox.com>; Pascal Mazon <pascal.ma...@6wind.com>; > > Ophir > > > Munk <ophi...@mellanox.com>; sta...@dpdk.org > > > Subject: [PATCH v1] gso: fix marking TCP checksum flag in TCP segments > > > > > > Large TCP packets which are marked with PKT_TX_TCP_SEG flag are > > > segmented and the flag is cleared in the resulting segments, however, > > > the segments checksum is not updated. It is therefore required to set > > > the PKT_TX_TCP_CKSUM flag in each TCP segment in order to mark for the > > > sending driver the need to update the TCP checksum before transmitting > > > the segment. > > > > > > Fixes: 119583797b6a ("gso: support TCP/IPv4 GSO") > > > Cc: sta...@dpdk.org > > > > > > Signed-off-by: Ophir Munk <ophi...@mellanox.com> > > > --- > > > lib/librte_gso/rte_gso.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/lib/librte_gso/rte_gso.c b/lib/librte_gso/rte_gso.c index > > > a44e3d4..e9ce9ce 100644 > > > --- a/lib/librte_gso/rte_gso.c > > > +++ b/lib/librte_gso/rte_gso.c > > > @@ -50,12 +50,14 @@ rte_gso_segment(struct rte_mbuf *pkt, > > > ((IS_IPV4_GRE_TCP4(pkt->ol_flags) && > > > (gso_ctx->gso_types & > > > DEV_TX_OFFLOAD_GRE_TNL_TSO)))) { > > > pkt->ol_flags &= (~PKT_TX_TCP_SEG); > > > + pkt->ol_flags |= PKT_TX_TCP_CKSUM; > > > ret = gso_tunnel_tcp4_segment(pkt, gso_size, ipid_delta, > > > direct_pool, indirect_pool, > > > pkts_out, nb_pkts_out); > > > } else if (IS_IPV4_TCP(pkt->ol_flags) && > > > (gso_ctx->gso_types & > > > DEV_TX_OFFLOAD_TCP_TSO)) { > > > pkt->ol_flags &= (~PKT_TX_TCP_SEG); > > > + pkt->ol_flags |= PKT_TX_TCP_CKSUM; > > > ret = gso_tcp4_segment(pkt, gso_size, ipid_delta, > > > direct_pool, indirect_pool, > > > pkts_out, nb_pkts_out); > > > -- > > > 2.7.4
