From 2855e4925416c5900a9c6cece11f4a2e56bf6e63 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 30 Jan 2026 21:02:57 +0000 Subject: [PATCH] ipv6: add some unlikely()/likely() clauses in ip6_output.c 1) daddr is unlikely a multicast in ip6_finish_output2(). 2) ip6_finish_output_gso_slowpath_drop() should not be called often. 3) ip6_fragment() should not be called often. 4) opt is unlikely to be set. 5) ip6_xmit() and ip6_forward() mostly sends not too big packets. 6) Most __ip6_make_skb() calls are for UDP packets, not ICMPV6 ones. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260130210303.3888261-3-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv6/ip6_output.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index e4bed95ae5bb..5c2cfcc3cf6e 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -80,7 +80,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * hdr = ipv6_hdr(skb); daddr = &hdr->daddr; - if (ipv6_addr_is_multicast(daddr)) { + if (unlikely(ipv6_addr_is_multicast(daddr))) { if (!(dev->flags & IFF_LOOPBACK) && sk_mc_loop(sk) && ((mroute6_is_socket(net, skb) && !(IP6CB(skb)->flags & IP6SKB_FORWARDED)) || @@ -179,8 +179,8 @@ ip6_finish_output_gso_slowpath_drop(struct net *net, struct sock *sk, static int ip6_finish_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned int mtu) { - if (!(IP6CB(skb)->flags & IP6SKB_FAKEJUMBO) && - !skb_gso_validate_network_len(skb, mtu)) + if (unlikely(!(IP6CB(skb)->flags & IP6SKB_FAKEJUMBO) && + !skb_gso_validate_network_len(skb, mtu))) return ip6_finish_output_gso_slowpath_drop(net, sk, skb, mtu); return ip6_finish_output2(net, sk, skb); @@ -202,8 +202,8 @@ static int __ip6_finish_output(struct net *net, struct sock *sk, struct sk_buff if (skb_is_gso(skb)) return ip6_finish_output_gso(net, sk, skb, mtu); - if (skb->len > mtu || - (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size)) + if (unlikely(skb->len > mtu || + (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size))) return ip6_fragment(net, sk, skb, ip6_finish_output2); return ip6_finish_output2(net, sk, skb); @@ -301,7 +301,7 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, } } - if (opt) { + if (unlikely(opt)) { seg_len += opt->opt_nflen + opt->opt_flen; if (opt->opt_flen) @@ -354,7 +354,7 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, skb->mark = mark; mtu = dst_mtu(dst); - if ((skb->len <= mtu) || skb->ignore_df || skb_is_gso(skb)) { + if (likely((skb->len <= mtu) || skb->ignore_df || skb_is_gso(skb))) { IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTREQUESTS); /* if egress device is enslaved to an L3 master device pass the @@ -654,7 +654,7 @@ int ip6_forward(struct sk_buff *skb) if (mtu < IPV6_MIN_MTU) mtu = IPV6_MIN_MTU; - if (ip6_pkt_too_big(skb, mtu)) { + if (unlikely(ip6_pkt_too_big(skb, mtu))) { /* Again, force OUTPUT device used as source address */ skb->dev = dev; icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu); @@ -1368,7 +1368,7 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, /* * setup for corking */ - if (opt) { + if (unlikely(opt)) { if (WARN_ON(v6_cork->opt)) return -EINVAL; @@ -1885,7 +1885,7 @@ static void ip6_cork_steal_dst(struct sk_buff *skb, struct inet_cork_full *cork) static void ip6_cork_release(struct inet_cork_full *cork, struct inet6_cork *v6_cork) { - if (v6_cork->opt) { + if (unlikely(v6_cork->opt)) { struct ipv6_txoptions *opt = v6_cork->opt; kfree(opt->dst0opt); @@ -1941,7 +1941,7 @@ struct sk_buff *__ip6_make_skb(struct sock *sk, __skb_pull(skb, skb_network_header_len(skb)); final_dst = &fl6->daddr; - if (opt) { + if (unlikely(opt)) { if (opt->opt_flen) proto = ipv6_push_frag_opts(skb, opt, proto); if (opt->opt_nflen) @@ -1969,7 +1969,7 @@ struct sk_buff *__ip6_make_skb(struct sock *sk, ip6_cork_steal_dst(skb, cork); IP6_INC_STATS(net, rt->rt6i_idev, IPSTATS_MIB_OUTREQUESTS); - if (proto == IPPROTO_ICMPV6) { + if (unlikely(proto == IPPROTO_ICMPV6)) { struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb)); u8 icmp6_type; -- 2.47.3