Richard Gobert wrote:
This commit utilizes a new helper function, ipv6_gro_pull_exthdrs, which is used in ipv6_gro_receive to pull ipv6 ext headers instead of ipv6_gso_pull_exthdrs. To use ipv6_gso_pull_exthdr, pskb_pull and __skb_push must be used, and frag0 must be invalidated. This commit removes unnecessary code around the call to ipv6_gso_pull_exthdrs and enables the frag0 fast path in IPv6 packets with ext headers.
Signed-off-by: Richard Gobert richardbgobert@gmail.com
net/ipv6/ip6_offload.c | 51 +++++++++++++++++++++++++++++++++--------- 1 file changed, 41 insertions(+), 10 deletions(-)
diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c index 0e0b5fed0995..a3b8d9127dbb 100644 --- a/net/ipv6/ip6_offload.c +++ b/net/ipv6/ip6_offload.c @@ -37,6 +37,40 @@ INDIRECT_CALL_L4(cb, f2, f1, head, skb); \ }) +static int ipv6_gro_pull_exthdrs(struct sk_buff *skb, int off, int proto) +{
- const struct net_offload *ops = NULL;
- struct ipv6_opt_hdr *opth;
- for (;;) {
int len;ops = rcu_dereference(inet6_offloads[proto]);if (unlikely(!ops))break;if (!(ops->flags & INET6_PROTO_GSO_EXTHDR))break;opth = skb_gro_header(skb, off + 8, off);
When changing this code, it would be great to make it more self documenting. It's not entirely clear what that 8 is based on. sizeof(*opth) is only 2. Probably an optimization to handle the most common extension headers in a single pskb_may_pull? If so, this new code does not have that concern, so can just use sizeof(*opth). Or else add a const int likely_max_opt_hdr_len = 8 or so.
if (unlikely(!opth))break;len = ipv6_optlen(opth);opth = skb_gro_header(skb, off + len, off);if (unlikely(!opth))break;proto = opth->nexthdr;off += len;- }
- skb_gro_pull(skb, off - skb_network_offset(skb));
- return proto;
+}
static int ipv6_gso_pull_exthdrs(struct sk_buff *skb, int proto) { const struct net_offload *ops = NULL; @@ -203,28 +237,25 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head, goto out; skb_set_network_header(skb, off);
- skb_gro_pull(skb, sizeof(*iph));
- skb_set_transport_header(skb, skb_gro_offset(skb));
- flush += ntohs(iph->payload_len) != skb_gro_len(skb);
- flush += ntohs(iph->payload_len) != skb->len - hlen;
proto = iph->nexthdr; ops = rcu_dereference(inet6_offloads[proto]); if (!ops || !ops->callbacks.gro_receive) {
pskb_pull(skb, skb_gro_offset(skb));skb_gro_frag0_invalidate(skb);proto = ipv6_gso_pull_exthdrs(skb, proto);skb_gro_pull(skb, -skb_transport_offset(skb));skb_reset_transport_header(skb);__skb_push(skb, skb_gro_offset(skb));
proto = ipv6_gro_pull_exthdrs(skb, hlen, proto);ops = rcu_dereference(inet6_offloads[proto]); if (!ops || !ops->callbacks.gro_receive) goto out;
iph = ipv6_hdr(skb);
iph = skb_gro_network_header(skb);- } else {
skb_gro_pull(skb, sizeof(*iph));
This code is non-obvious and has proven fragile (57ea52a8651). Changes are best as simple as they can be, with ample documentation. My attempt, as arrived at during review:
The existing always pulls the IPv6 header and sets the transport offset initially. Then optionally again pulls any extension headers in ipv6_gso_pull_exthdrs and sets the transport offset again on return from that call.
The new code adds a small optimization to only pull and set transport offset once.
The existing code needs to set skb->data at the start of the first extension header before calling ipv6_gso_pull_exthdrs, and must disable the frag0 optimization because that function uses pskb_may_pull/pskb_pull instead of skb_gro_ helpers. It sets the GRO offset to the inner TCP header with skb_gro_pull and sets the transport header. Then returns skb->data to its position before this block.
The new code is much simpler: it does not have to modify skb->data, as all operations are with skb_gro_ helpers.
Aside from the small comment above, and suggestion to include something like this summary in the code and/or avoid the extra optimization,
Reviewed-by: Willem de Bruijn willemb@google.com
- skb_set_transport_header(skb, skb_gro_offset(skb));
- NAPI_GRO_CB(skb)->proto = proto;
flush--; -- 2.36.1