From 219badfaade986a2c3d99abd4eb6d83f4f9ed2fb Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 31 Mar 2018 12:58:59 -0700 Subject: [PATCH] ipv6: frags: get rid of ip6frag_skb_cb/FRAG6_CB ip6_frag_queue uses skb->cb[] to store the fragment offset, meaning that we could use two cache lines per skb when finding the insertion point, if for some reason inet6_skb_parm size is increased in the future. By using skb->ip_defrag_offset instead of skb->cb[], we pack all the fields in a single cache line, matching what we did for IPv4. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/reassembly.c | 30 ++++++++++++------------------ 1 file changed, 12 insertions(+), 18 deletions(-) diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c index 2127da130dc2..7b52efc63f6a 100644 --- a/net/ipv6/reassembly.c +++ b/net/ipv6/reassembly.c @@ -62,13 +62,6 @@ static const char ip6_frag_cache_name[] = "ip6-frags"; -struct ip6frag_skb_cb { - struct inet6_skb_parm h; - int offset; -}; - -#define FRAG6_CB(skb) ((struct ip6frag_skb_cb *)((skb)->cb)) - static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h) { return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK); @@ -250,13 +243,13 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb, * this fragment, right? */ prev = fq->q.fragments_tail; - if (!prev || FRAG6_CB(prev)->offset < offset) { + if (!prev || prev->ip_defrag_offset < offset) { next = NULL; goto found; } prev = NULL; for (next = fq->q.fragments; next != NULL; next = next->next) { - if (FRAG6_CB(next)->offset >= offset) + if (next->ip_defrag_offset >= offset) break; /* bingo! */ prev = next; } @@ -271,14 +264,20 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb, /* Check for overlap with preceding fragment. */ if (prev && - (FRAG6_CB(prev)->offset + prev->len) > offset) + (prev->ip_defrag_offset + prev->len) > offset) goto discard_fq; /* Look for overlap with succeeding segment. */ - if (next && FRAG6_CB(next)->offset < end) + if (next && next->ip_defrag_offset < end) goto discard_fq; - FRAG6_CB(skb)->offset = offset; + /* Note : skb->ip_defrag_offset and skb->dev share the same location */ + dev = skb->dev; + if (dev) + fq->iif = dev->ifindex; + /* Makes sure compiler wont do silly aliasing games */ + barrier(); + skb->ip_defrag_offset = offset; /* Insert this fragment in the chain of fragments. */ skb->next = next; @@ -289,11 +288,6 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb, else fq->q.fragments = skb; - dev = skb->dev; - if (dev) { - fq->iif = dev->ifindex; - skb->dev = NULL; - } fq->q.stamp = skb->tstamp; fq->q.meat += skb->len; fq->ecn |= ecn; @@ -380,7 +374,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev, } WARN_ON(head == NULL); - WARN_ON(FRAG6_CB(head)->offset != 0); + WARN_ON(head->ip_defrag_offset != 0); /* Unfragmented part is taken from the first segment. */ payload_len = ((head->data - skb_network_header(head)) - -- GitLab