On Thu, Jan 05, 2023 at 06:55:03PM +0530, Hemanth Aramadaka via dev wrote:
> Issue:
>
> The src-port for UDP is based on RSS hash in the packet metadata.
> In case of packets coming from VM it will be 5-tuple, if available,
> otherwise just IP addresses.If the VM fragments a large IP packet
> and sends the fragments to ovs, only the first fragment will contain
> the L4 header. Therefore, the first fragment and subsequent fragments
> get different UDP src ports in the outgoing VXLAN header.This can
> lead to fragment re-ordering in the fabric as packet will take
> different paths.
>
> Fix:
>
> Intention of this is to avoid fragment packets taking different paths.
> For example, due to presence of firewalls, fragment packets will take
> different paths and will get dropped.To avoid this we ignore the L4
> header during hash calculation only in the case of fragmented packets.
>
> Signed-off-by: Hemanth Aramadaka <[email protected]>
> ---
> lib/flow.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/lib/flow.c b/lib/flow.c
> index c3a3aa3ce..4f4197b1c 100644
> --- a/lib/flow.c
> +++ b/lib/flow.c
> @@ -1018,7 +1018,9 @@ miniflow_extract(struct dp_packet *packet, struct
> miniflow *dst)
> miniflow_push_be16(mf, ct_tp_src, ct_tp_src);
> miniflow_push_be16(mf, ct_tp_dst, ct_tp_dst);
> if (dl_type == htons(ETH_TYPE_IP)) {
> - dp_packet_update_rss_hash_ipv4_tcp_udp(packet);
> + if (!(nw_frag & FLOW_NW_FRAG_MASK)) {
> + dp_packet_update_rss_hash_ipv4_tcp_udp(packet);
> + }
> } else if (dl_type == htons(ETH_TYPE_IPV6)) {
> dp_packet_update_rss_hash_ipv6_tcp_udp(packet);
> }
> @@ -1033,7 +1035,9 @@ miniflow_extract(struct dp_packet *packet, struct
> miniflow *dst)
> miniflow_push_be16(mf, ct_tp_src, ct_tp_src);
> miniflow_push_be16(mf, ct_tp_dst, ct_tp_dst);
> if (dl_type == htons(ETH_TYPE_IP)) {
> - dp_packet_update_rss_hash_ipv4_tcp_udp(packet);
> + if (!(nw_frag & FLOW_NW_FRAG_MASK)) {
> + dp_packet_update_rss_hash_ipv4_tcp_udp(packet);
> + }
> } else if (dl_type == htons(ETH_TYPE_IPV6)) {
> dp_packet_update_rss_hash_ipv6_tcp_udp(packet);
> }
> @@ -2248,7 +2252,7 @@ miniflow_hash_5tuple(const struct miniflow *flow,
> uint32_t basis)
>
> if (flow) {
> ovs_be16 dl_type = MINIFLOW_GET_BE16(flow, dl_type);
> - uint8_t nw_proto;
> + uint8_t nw_proto, nw_frag;
>
> if (dl_type == htons(ETH_TYPE_IPV6)) {
> struct flowmap map = FLOWMAP_EMPTY_INITIALIZER;
> @@ -2270,6 +2274,14 @@ miniflow_hash_5tuple(const struct miniflow *flow,
> uint32_t basis)
>
> nw_proto = MINIFLOW_GET_U8(flow, nw_proto);
> hash = hash_add(hash, nw_proto);
> +
> + /* Skip l4 header fields if IP packet is fragmented since
> + * only first fragment will carry l4 header.
> + */
> + nw_frag = MINIFLOW_GET_U8(flow, nw_frag);
> + if (nw_frag & FLOW_NW_FRAG_MASK) {
> + goto out;
> + }
Maybe I am reading things wrong, but it seems to me that
this change seems to effect all protocols, and in particular both
IPv4 and IPv6. Whereas the changes above to miniflow_extract()
only affect IPv6. Is this intentional?
> if (nw_proto != IPPROTO_TCP && nw_proto != IPPROTO_UDP
> && nw_proto != IPPROTO_SCTP && nw_proto != IPPROTO_ICMP
> && nw_proto != IPPROTO_ICMPV6) {
> --
> 2.34.1
>
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> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>
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