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ipv6: frags: get rid of ip6frag_skb_cb/FRAG6_CB

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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 <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-03-31 12:58:59 -07:00 committed by David S. Miller
parent bf66337140
commit 219badfaad
1 changed files with 12 additions and 18 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

30
net/ipv6/reassembly.c
View file

@ -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)) -