On Mon, Jul 1, 2024 at 6:25 AM junwang01--- via discuss
<ovs-discuss@openvswitch.org> wrote:
>
> Hi,team.
> Some switches add padding bytes to packets smaller than 64 bytes that are
> sent from outside.
> However, in our netdev_tnl_push_ip_header processing, we directly set
> l2_pad_size to 0.
> I believe that l2_pad_size should be reassigned with the value it originally
> carried.
> After making this modification, the L4 checksum for my inner packets became
> correct.
>
> https://github.com/openvswitch/ovs/blob/main/lib/netdev-native-tnl.c#L166
>
> Currently, I can resolve the issue with the following modification, but I am
> unsure if this
> approach is the most correct, or if there are other places that also need the
> same modification.
>
> diff --git a/lib/netdev-native-tnl.c b/lib/netdev-native-tnl.c
> index dd598ce31..1084dbe91 100644
> --- a/lib/netdev-native-tnl.c
> +++ b/lib/netdev-native-tnl.c
> @@ -163,7 +163,9 @@ netdev_tnl_push_ip_header(struct dp_packet *packet,
> memcpy(eth, header, size);
> /* The encapsulated packet has type Ethernet. Adjust dp_packet. */
> packet->packet_type = htonl(PT_ETH);
> + uint16_t l2_pad_size = packet->l2_pad_size;
> dp_packet_reset_offsets(packet);
> + packet->l2_pad_size = l2_pad_size;
> packet->l3_ofs = sizeof (struct eth_header);
I don't think we need to carry this padding over a tunnel.
I did not test but I wonder if adjusting ip_tot_size is better.
Something like:
@@ -158,7 +158,8 @@ netdev_tnl_push_ip_header(struct dp_packet
*packet, const void *header,
struct ovs_16aligned_ip6_hdr *ip6;
eth = dp_packet_push_uninit(packet, size);
- *ip_tot_size = dp_packet_size(packet) - sizeof (struct eth_header);
+ *ip_tot_size = dp_packet_size(packet) - dp_packet_l2_pad_size(packet)
+ - sizeof (struct eth_header);
memcpy(eth, header, size);
/* The encapsulated packet has type Ethernet. Adjust dp_packet. */
--
David Marchand
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