Commit dce52518 authored by Justin Iurman's avatar Justin Iurman Committed by Paolo Abeni
Browse files

net: ipv6: ioam6_iptunnel: mitigate 2-realloc issue 

This patch mitigates the two-reallocations issue with ioam6_iptunnel by
providing the dst_entry (in the cache) to the first call to
skb_cow_head(). As a result, the very first iteration may still trigger
two reallocations (i.e., empty cache), while next iterations would only
trigger a single reallocation.

Performance tests before/after applying this patch, which clearly shows
the improvement:
- inline mode:
  - before: https://ibb.co/LhQ8V63
  - after: https://ibb.co/x5YT2bS
- encap mode:
  - before: https://ibb.co/3Cjm5m0
  - after: https://ibb.co/TwpsxTC
- encap mode with tunsrc:
  - before: https://ibb.co/Gpy9QPg
  - after: https://ibb.co/PW1bZFT



This patch also fixes an incorrect behavior: after the insertion, the
second call to skb_cow_head() makes sure that the dev has enough
headroom in the skb for layer 2 and stuff. In that case, the "old"
dst_entry was used, which is now fixed. After discussing with Paolo, it
appears that both patches can be merged into a single one -this one-
(for the sake of readability) and target net-next.

Signed-off-by: default avatarJustin Iurman <justin.iurman@uliege.be>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 0600cf40

net/ipv6/ioam6_iptunnel.c

+37 −36
Original line number Diff line number Diff line
@@ -253,14 +253,15 @@ static int ioam6_do_fill(struct net *net, struct sk_buff *skb) 
}



static int ioam6_do_inline(struct net *net, struct sk_buff *skb,

			   struct ioam6_lwt_encap *tuninfo)

			   struct ioam6_lwt_encap *tuninfo,

			   struct dst_entry *cache_dst)

{

	struct ipv6hdr *oldhdr, *hdr;

	int hdrlen, err;



	hdrlen = (tuninfo->eh.hdrlen + 1) << 3;



	err = skb_cow_head(skb, hdrlen + skb->mac_len);

	err = skb_cow_head(skb, hdrlen + dst_dev_overhead(cache_dst, skb));

	if (unlikely(err))

		return err;
@@ -291,7 +292,8 @@ static int ioam6_do_encap(struct net *net, struct sk_buff *skb, 
			  struct ioam6_lwt_encap *tuninfo,

			  bool has_tunsrc,

			  struct in6_addr *tunsrc,

			  struct in6_addr *tundst)

			  struct in6_addr *tundst,

			  struct dst_entry *cache_dst)

{

	struct dst_entry *dst = skb_dst(skb);

	struct ipv6hdr *hdr, *inner_hdr;
@@ -300,7 +302,7 @@ static int ioam6_do_encap(struct net *net, struct sk_buff *skb, 
	hdrlen = (tuninfo->eh.hdrlen + 1) << 3;

	len = sizeof(*hdr) + hdrlen;



	err = skb_cow_head(skb, len + skb->mac_len);

	err = skb_cow_head(skb, len + dst_dev_overhead(cache_dst, skb));

	if (unlikely(err))

		return err;
@@ -334,7 +336,7 @@ static int ioam6_do_encap(struct net *net, struct sk_buff *skb, 


static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb)

{

	struct dst_entry *dst = skb_dst(skb);

	struct dst_entry *dst = skb_dst(skb), *cache_dst;

	struct in6_addr orig_daddr;

	struct ioam6_lwt *ilwt;

	int err = -EINVAL;
@@ -352,6 +354,10 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb) 


	orig_daddr = ipv6_hdr(skb)->daddr;



	local_bh_disable();

	cache_dst = dst_cache_get(&ilwt->cache);

	local_bh_enable();



	switch (ilwt->mode) {

	case IOAM6_IPTUNNEL_MODE_INLINE:

do_inline:
@@ -359,7 +365,7 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb) 
		if (ipv6_hdr(skb)->nexthdr == NEXTHDR_HOP)

			goto out;



		err = ioam6_do_inline(net, skb, &ilwt->tuninfo);

		err = ioam6_do_inline(net, skb, &ilwt->tuninfo, cache_dst);

		if (unlikely(err))

			goto drop;
@@ -369,7 +375,7 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb) 
		/* Encapsulation (ip6ip6) */

		err = ioam6_do_encap(net, skb, &ilwt->tuninfo,

				     ilwt->has_tunsrc, &ilwt->tunsrc,

				     &ilwt->tundst);

				     &ilwt->tundst, cache_dst);

		if (unlikely(err))

			goto drop;
@@ -387,16 +393,7 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb) 
		goto drop;

	}



	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));

	if (unlikely(err))

		goto drop;



	if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {

		local_bh_disable();

		dst = dst_cache_get(&ilwt->cache);

		local_bh_enable();



		if (unlikely(!dst)) {

	if (unlikely(!cache_dst)) {

		struct ipv6hdr *hdr = ipv6_hdr(skb);

		struct flowi6 fl6;
@@ -407,21 +404,25 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb) 
		fl6.flowi6_mark = skb->mark;

		fl6.flowi6_proto = hdr->nexthdr;



			dst = ip6_route_output(net, NULL, &fl6);

			if (dst->error) {

				err = dst->error;

				dst_release(dst);

		cache_dst = ip6_route_output(net, NULL, &fl6);

		if (cache_dst->error) {

			err = cache_dst->error;

			dst_release(cache_dst);

			goto drop;

		}



		local_bh_disable();

			dst_cache_set_ip6(&ilwt->cache, dst, &fl6.saddr);

		dst_cache_set_ip6(&ilwt->cache, cache_dst, &fl6.saddr);

		local_bh_enable();



		err = skb_cow_head(skb, LL_RESERVED_SPACE(cache_dst->dev));

		if (unlikely(err))

			goto drop;

	}



	if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {

		skb_dst_drop(skb);

		skb_dst_set(skb, dst);



		skb_dst_set(skb, cache_dst);

		return dst_output(net, sk, skb);

	}

out: