On Fri, Oct 19, 2018 at 04:25:12PM +0200, Paolo Abeni wrote:
>
> +#define UDO_GRO_CNT_MAX 64
Maybe better UDP_GRO_CNT_MAX?
Btw. do we really need this explicit limit?
We should not get more than 64 packets during
one napi poll cycle.
> +static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
> + struct sk_buff *skb)
> +{
> + struct udphdr *uh = udp_hdr(skb);
> + struct sk_buff *pp = NULL;
> + struct udphdr *uh2;
> + struct sk_buff *p;
> +
> + /* requires non zero csum, for simmetry with GSO */
> + if (!uh->check) {
> + NAPI_GRO_CB(skb)->flush = 1;
> + return NULL;
> + }
Why is the requirement of checksums different than in
udp_gro_receive? It's not that I care much about UDP
packets without a checksum, but you would not need
to implement your own loop if the requirement could
be the same as in udp_gro_receive.
> +
> + /* pull encapsulating udp header */
> + skb_gro_pull(skb, sizeof(struct udphdr));
> + skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
> +
> + list_for_each_entry(p, head, list) {
> + if (!NAPI_GRO_CB(p)->same_flow)
> + continue;
> +
> + uh2 = udp_hdr(p);
> +
> + /* Match ports only, as csum is always non zero */
> + if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
> + NAPI_GRO_CB(p)->same_flow = 0;
> + continue;
> + }
> +
> + /* Terminate the flow on len mismatch or if it grow "too much".
> + * Under small packet flood GRO count could elsewhere grow a lot
> + * leading to execessive truesize values
> + */
> + if (!skb_gro_receive(p, skb) &&
> + NAPI_GRO_CB(p)->count > UDO_GRO_CNT_MAX)
This allows to merge UDO_GRO_CNT_MAX + 1 packets.
> + pp = p;
> + else if (uh->len != uh2->len)
> + pp = p;
> +
> + return pp;
> + }
> +
> + /* mismatch, but we never need to flush */
> + return NULL;
> +}
