> From: Ferruh Yigit [mailto:ferruh.yi...@intel.com] > Sent: Tuesday, November 10, 2020 6:43 PM > > On 11/10/2020 4:01 PM, Morten Brørup wrote: > >> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Ferruh Yigit > >> Sent: Tuesday, November 10, 2020 3:47 PM > >> > >> On 11/9/2020 2:22 PM, Michael Pfeiffer wrote: > >>> Unlike TCP, UDP checksums are optional and may be zero to indicate > "not > >>> set" [RFC 768] (except for IPv6, where this prohibited [RFC 8200]). > Add > >>> this special case to the checksum offload emulation in net/tap. > >>> > >>> Signed-off-by: Michael Pfeiffer <michael.pfeif...@tu-ilmenau.de> > >>> --- > >>> drivers/net/tap/rte_eth_tap.c | 13 +++++++++++-- > >>> 1 file changed, 11 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/net/tap/rte_eth_tap.c > >> b/drivers/net/tap/rte_eth_tap.c > >>> index 2f8abb12c..e486b41c5 100644 > >>> --- a/drivers/net/tap/rte_eth_tap.c > >>> +++ b/drivers/net/tap/rte_eth_tap.c > >>> @@ -303,6 +303,7 @@ tap_verify_csum(struct rte_mbuf *mbuf) > >>> uint16_t cksum = 0; > >>> void *l3_hdr; > >>> void *l4_hdr; > >>> + struct rte_udp_hdr *udp_hdr; > >>> > >>> if (l2 == RTE_PTYPE_L2_ETHER_VLAN) > >>> l2_len += 4; > >>> @@ -349,10 +350,18 @@ tap_verify_csum(struct rte_mbuf *mbuf) > >>> /* Don't verify checksum for multi-segment packets. > */ > >>> if (mbuf->nb_segs > 1) > >>> return; > >>> - if (l3 == RTE_PTYPE_L3_IPV4) > >>> + if (l3 == RTE_PTYPE_L3_IPV4) { > >>> + if (l4 == RTE_PTYPE_L4_UDP) { > >>> + udp_hdr = (struct rte_udp_hdr *)l4_hdr; > >>> + if (udp_hdr->dgram_cksum == 0) { > >>> + mbuf->ol_flags |= PKT_RX_L4_CKSUM_NONE; > >>> + return; > >>> + } > >>> + } > >>> cksum = ~rte_ipv4_udptcp_cksum(l3_hdr, l4_hdr); > >>> - else if (l3 == RTE_PTYPE_L3_IPV6) > >>> + } else if (l3 == RTE_PTYPE_L3_IPV6) { > >>> cksum = ~rte_ipv6_udptcp_cksum(l3_hdr, l4_hdr); > >>> + } > >>> mbuf->ol_flags |= cksum ? > >>> PKT_RX_L4_CKSUM_BAD : > >>> PKT_RX_L4_CKSUM_GOOD; > >>> > >> > >> While checking this I stuck with following part: > >> > >> cksum = ~rte_ipv6_udptcp_cksum(l3_hdr, l4_hdr); > >> ... > >> mbuf->ol_flags |= cksum ? > >> PKT_RX_L4_CKSUM_BAD : > >> PKT_RX_L4_CKSUM_GOOD; > >> > >> > >> Is this correct, or am I missing something, can intention be '!' > here > >> instead of > >> '~' ? > > > > It is correct. The packet's checksum is calculated by > rte_ipv6_udptcp_cksum(), and it should be 0xFFFF. The '~' operation > makes cksum 0 iff the calculated checksum is 0xFFFF. > > > > Yep, figure that out late, > as far as I understand when the checksum value is zero, > 'rte_ipv6_udptcp_cksum()' will return the checksum value and when > checksum is > correct in the packet, function will return 0xFFFF, this is based on > checksum > calculation, is this right?
Exactly.
