Hi,
On Tue, 2020-11-10 at 15:59 +0000, Ferruh Yigit wrote:
> 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) {
>
> Overall patch looks good to me, but can you please add a comment on top of
> above
> check to describe why checksum can be zero, as done in the commit log.
Sure, I will update the patch. I am also not completely sure whether
PKT_RX_L4_CKSUM_NONE is the right flag for this case (rather than _UNKNOWN).
>From rte_core_mbuf.h:
* - PKT_RX_L4_CKSUM_UNKNOWN: no information about the RX L4 checksum
* - PKT_RX_L4_CKSUM_NONE: the L4 checksum is not correct in the packet
* data, but the integrity of the L4 data is verified.
The second part after the "but" is not really the case here. I don't know how
relevant the distinction is, as most application side code will probably only
do something like
if ((mbuf->ol_flags & PKT_RX_L4_CKSUM_MASK) == PKT_RX_L4_CKSUM_BAD)
rte_pktmbuf_free(mbuf);
anyway. Do you have any opinions on that?
> > + 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;
> >
>
Regards
Michael
