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 <eduma...@google.com>
---
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
2127da130dc2cee677059247d5e079a8afbca13d..7b52efc63f6adad2c242ae1171e5b7b27b40f0bf
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)) -
--
2.17.0.rc1.321.gba9d0f2565-goog
