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?
