Commit 40475b63 authored by Justin Iurman's avatar Justin Iurman Committed by Paolo Abeni
Browse files

net: ipv6: seg6_iptunnel: mitigate 2-realloc issue 

This patch mitigates the two-reallocations issue with seg6_iptunnel by
providing the dst_entry (in the cache) to the first call to
skb_cow_head(). As a result, the very first iteration would 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:
- before: https://ibb.co/3Cg4sNH
- after: https://ibb.co/8rQ350r



Signed-off-by: default avatarJustin Iurman <justin.iurman@uliege.be>
Cc: David Lebrun <dlebrun@google.com>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent dce52518

net/ipv6/seg6_iptunnel.c

+52 −33
Original line number Diff line number Diff line
@@ -124,8 +124,8 @@ static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb, 
	return flowlabel;

}



/* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */

int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)

static int __seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh,

			       int proto, struct dst_entry *cache_dst)

{

	struct dst_entry *dst = skb_dst(skb);

	struct net *net = dev_net(dst->dev);
@@ -137,7 +137,7 @@ int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto) 
	hdrlen = (osrh->hdrlen + 1) << 3;

	tot_len = hdrlen + sizeof(*hdr);



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

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

	if (unlikely(err))

		return err;
@@ -197,11 +197,18 @@ int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto) 


	return 0;

}



/* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */

int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)

{

	return __seg6_do_srh_encap(skb, osrh, proto, NULL);

}

EXPORT_SYMBOL_GPL(seg6_do_srh_encap);



/* encapsulate an IPv6 packet within an outer IPv6 header with reduced SRH */

static int seg6_do_srh_encap_red(struct sk_buff *skb,

				 struct ipv6_sr_hdr *osrh, int proto)

				 struct ipv6_sr_hdr *osrh, int proto,

				 struct dst_entry *cache_dst)

{

	__u8 first_seg = osrh->first_segment;

	struct dst_entry *dst = skb_dst(skb);
@@ -230,7 +237,7 @@ static int seg6_do_srh_encap_red(struct sk_buff *skb, 


	tot_len = red_hdrlen + sizeof(struct ipv6hdr);



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

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

	if (unlikely(err))

		return err;
@@ -317,8 +324,8 @@ static int seg6_do_srh_encap_red(struct sk_buff *skb, 
	return 0;

}



/* insert an SRH within an IPv6 packet, just after the IPv6 header */

int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)

static int __seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh,

				struct dst_entry *cache_dst)

{

	struct ipv6hdr *hdr, *oldhdr;

	struct ipv6_sr_hdr *isrh;
@@ -326,7 +333,7 @@ int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh) 


	hdrlen = (osrh->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;
@@ -369,9 +376,8 @@ int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh) 


	return 0;

}

EXPORT_SYMBOL_GPL(seg6_do_srh_inline);



static int seg6_do_srh(struct sk_buff *skb)

static int seg6_do_srh(struct sk_buff *skb, struct dst_entry *cache_dst)

{

	struct dst_entry *dst = skb_dst(skb);

	struct seg6_iptunnel_encap *tinfo;
@@ -384,7 +390,7 @@ static int seg6_do_srh(struct sk_buff *skb) 
		if (skb->protocol != htons(ETH_P_IPV6))

			return -EINVAL;



		err = seg6_do_srh_inline(skb, tinfo->srh);

		err = __seg6_do_srh_inline(skb, tinfo->srh, cache_dst);

		if (err)

			return err;

		break;
@@ -402,9 +408,11 @@ static int seg6_do_srh(struct sk_buff *skb) 
			return -EINVAL;



		if (tinfo->mode == SEG6_IPTUN_MODE_ENCAP)

			err = seg6_do_srh_encap(skb, tinfo->srh, proto);

			err = __seg6_do_srh_encap(skb, tinfo->srh,

						  proto, cache_dst);

		else

			err = seg6_do_srh_encap_red(skb, tinfo->srh, proto);

			err = seg6_do_srh_encap_red(skb, tinfo->srh,

						    proto, cache_dst);



		if (err)

			return err;
@@ -425,11 +433,13 @@ static int seg6_do_srh(struct sk_buff *skb) 
		skb_push(skb, skb->mac_len);



		if (tinfo->mode == SEG6_IPTUN_MODE_L2ENCAP)

			err = seg6_do_srh_encap(skb, tinfo->srh,

						IPPROTO_ETHERNET);

			err = __seg6_do_srh_encap(skb, tinfo->srh,

						  IPPROTO_ETHERNET,

						  cache_dst);

		else

			err = seg6_do_srh_encap_red(skb, tinfo->srh,

						    IPPROTO_ETHERNET);

						    IPPROTO_ETHERNET,

						    cache_dst);



		if (err)

			return err;
@@ -444,6 +454,13 @@ static int seg6_do_srh(struct sk_buff *skb) 
	return 0;

}



/* insert an SRH within an IPv6 packet, just after the IPv6 header */

int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)

{

	return __seg6_do_srh_inline(skb, osrh, NULL);

}

EXPORT_SYMBOL_GPL(seg6_do_srh_inline);



static int seg6_input_finish(struct net *net, struct sock *sk,

			     struct sk_buff *skb)

{
@@ -458,31 +475,33 @@ static int seg6_input_core(struct net *net, struct sock *sk, 
	struct seg6_lwt *slwt;

	int err;



	err = seg6_do_srh(skb);

	if (unlikely(err))

		goto drop;



	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);



	local_bh_disable();

	dst = dst_cache_get(&slwt->cache);

	local_bh_enable();



	err = seg6_do_srh(skb, dst);

	if (unlikely(err))

		goto drop;



	if (!dst) {

		ip6_route_input(skb);

		dst = skb_dst(skb);

		if (!dst->error) {

			local_bh_disable();

			dst_cache_set_ip6(&slwt->cache, dst,

					  &ipv6_hdr(skb)->saddr);

		}

	} else {

		skb_dst_drop(skb);

		skb_dst_set(skb, dst);

	}

			local_bh_enable();

		}



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

		if (unlikely(err))

			goto drop;

	} else {

		skb_dst_drop(skb);

		skb_dst_set(skb, dst);

	}



	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))

		return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
@@ -528,16 +547,16 @@ static int seg6_output_core(struct net *net, struct sock *sk, 
	struct seg6_lwt *slwt;

	int err;



	err = seg6_do_srh(skb);

	if (unlikely(err))

		goto drop;



	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);



	local_bh_disable();

	dst = dst_cache_get(&slwt->cache);

	local_bh_enable();



	err = seg6_do_srh(skb, dst);

	if (unlikely(err))

		goto drop;



	if (unlikely(!dst)) {

		struct ipv6hdr *hdr = ipv6_hdr(skb);

		struct flowi6 fl6;
@@ -559,14 +578,14 @@ static int seg6_output_core(struct net *net, struct sock *sk, 
		local_bh_disable();

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

		local_bh_enable();

	}



	skb_dst_drop(skb);

	skb_dst_set(skb, dst);



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

		if (unlikely(err))

			goto drop;

	}



	skb_dst_drop(skb);

	skb_dst_set(skb, dst);



	if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))

		return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk, skb,