Messages in this thread | | | Date | Tue, 23 Apr 2024 11:27:22 +0200 | Subject | Re: [PATCH net v2 1/3] net: gro: add {inner_}network_offset to napi_gro_cb | From | Richard Gobert <> |
| |
Willem de Bruijn wrote: > Richard Gobert wrote: >> Willem de Bruijn wrote: >>> Richard Gobert wrote: >>>> This patch adds network_offset and inner_network_offset to napi_gro_cb, and >>>> makes sure both are set correctly. In the common path there's only one >>>> write (skb_gro_reset_offset, which replaces skb_set_network_header). >>>> >>>> Signed-off-by: Richard Gobert <richardbgobert@gmail.com> >>>> --- >>>> drivers/net/geneve.c | 1 + >>>> drivers/net/vxlan/vxlan_core.c | 1 + >>>> include/net/gro.h | 18 ++++++++++++++++-- >>>> net/8021q/vlan_core.c | 2 ++ >>>> net/core/gro.c | 1 + >>>> net/ethernet/eth.c | 1 + >>>> net/ipv4/af_inet.c | 5 +---- >>>> net/ipv4/gre_offload.c | 1 + >>>> net/ipv6/ip6_offload.c | 8 ++++---- >>>> 9 files changed, 28 insertions(+), 10 deletions(-) >>>> >>> >>>> +static inline int skb_gro_network_offset(const struct sk_buff *skb) >>>> +{ >>>> + return NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark]; >>>> +} >>>> + >>> >>> >>>> @@ -236,8 +236,6 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head, >>>> if (unlikely(!iph)) >>>> goto out; >>>> >>>> - skb_set_network_header(skb, off); >>>> - >>> >>> Especially for net, this is still a large patch. >>> >>> Can we avoid touching all those tunnel callbacks and just set the >>> offsets in inet_gro_receive and ipv6_gro_receive themselves, just >>> as skb_set_network_header now: >>> >>> @@ -236,7 +236,7 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head, >>> if (unlikely(!iph)) >>> goto out; >>> >>> - skb_set_network_header(skb, off); >>> + NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark] = off; >>> >> >> Thanks for the reply! >> >> Setting network_offset on dev_gro_receive and inner_network_offset only >> in the tunnel callbacks is the best option IMO. I agree that >> we want a small patch to net that solves the problem, although I >> think always using ->encap_mark in the common path is not ideal. >> >> We can avoid changing all the tunnel callbacks by always setting >> inner_network_offset in {ipv6,inet}_gro_receive and initialize >> network_offset to 0 in dev_gro_receive. It will result in a small >> change, without using ->encap_mark. >> >> What are your thoughts? > > That works. It's a bit ugly that inner_network_offset will always be > set, even if a packet only traverses inet_gro_receive once. What is > your concern with testing encap_mark? > > How do you want to detect in udp[46]_lib_lookup_skb which of the two > offsets to use? That would still be encap_mark based? >
I'd like to minimize any potential overhead, even a small one, and this way we do not need to access encap_mark at all in the common path.
NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark] = off;
compiles to:
movzx eax, byte ptr [rbx+46h] shr al, 1 and eax, 1 mov [rbx+rax*2+4Ch], r14w
while
NAPI_GRO_CB(skb)->inner_network_offset = off;
compiles to:
mov [rbx+4Eh], r14w
I do plan to add a patch to net-next after this to remove the access entirely from inet gro callbacks, in the meantime, it looks to me like a reasonable patch and small enough to not raise concerns.
For udp_lib_lookup I don't see a way around it so yes, it would still be dependent on encap_mark. Since this runs in the complete phase it's less concerning.
Let me know that you're ok with that and I'll post a v3.
| |