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net: ipv6: seg6_iptunnel: mitigate 2-realloc issue

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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: Justin Iurman <justin.iurman@uliege.be>
Cc: David Lebrun <dlebrun@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Justin Iurman 2024-12-03 13:49:44 +01:00 • committed by Paolo Abeni
parent dce525185b
commit 40475b6376
1 changed files with 52 additions and 33 deletions
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85
net/ipv6/seg6_iptunnel.c
View file

@ -124,8 +124,8 @@ static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb,
return flowlabel; return flowlabel;
} }
/* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */ static int __seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh,
int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto) int proto, struct dst_entry *cache_dst)
{ {
struct dst_entry *dst = skb_dst(skb); struct dst_entry *dst = skb_dst(skb);
struct net *net = dev_net(dst->dev); 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; hdrlen = (osrh->hdrlen + 1) << 3;
tot_len = hdrlen + sizeof(*hdr); 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)) if (unlikely(err))
return 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; 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); EXPORT_SYMBOL_GPL(seg6_do_srh_encap);
/* encapsulate an IPv6 packet within an outer IPv6 header with reduced SRH */ /* encapsulate an IPv6 packet within an outer IPv6 header with reduced SRH */
static int seg6_do_srh_encap_red(struct sk_buff *skb, 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; __u8 first_seg = osrh->first_segment;
struct dst_entry *dst = skb_dst(skb); 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); 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)) if (unlikely(err))
return err; return err;
@ -317,8 +324,8 @@ out:
return 0; return 0;
} }
/* insert an SRH within an IPv6 packet, just after the IPv6 header */ static int __seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh,
int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh) struct dst_entry *cache_dst)
{ {
struct ipv6hdr *hdr, *oldhdr; struct ipv6hdr *hdr, *oldhdr;
struct ipv6_sr_hdr *isrh; 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; 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)) if (unlikely(err))
return err; return err;
@ -369,9 +376,8 @@ int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
return 0; 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 dst_entry *dst = skb_dst(skb);
struct seg6_iptunnel_encap *tinfo; 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)) if (skb->protocol != htons(ETH_P_IPV6))
return -EINVAL; return -EINVAL;
err = seg6_do_srh_inline(skb, tinfo->srh); err = __seg6_do_srh_inline(skb, tinfo->srh, cache_dst);
if (err) if (err)
return err; return err;
break; break;
@ -402,9 +408,11 @@ static int seg6_do_srh(struct sk_buff *skb)
return -EINVAL; return -EINVAL;
if (tinfo->mode == SEG6_IPTUN_MODE_ENCAP) 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 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) if (err)
return err; return err;
@ -425,11 +433,13 @@ static int seg6_do_srh(struct sk_buff *skb)
skb_push(skb, skb->mac_len); skb_push(skb, skb->mac_len);
if (tinfo->mode == SEG6_IPTUN_MODE_L2ENCAP) if (tinfo->mode == SEG6_IPTUN_MODE_L2ENCAP)
err = seg6_do_srh_encap(skb, tinfo->srh, err = __seg6_do_srh_encap(skb, tinfo->srh,
IPPROTO_ETHERNET); IPPROTO_ETHERNET,
cache_dst);
else else
err = seg6_do_srh_encap_red(skb, tinfo->srh, err = seg6_do_srh_encap_red(skb, tinfo->srh,
IPPROTO_ETHERNET); IPPROTO_ETHERNET,
cache_dst);
if (err) if (err)
return err; return err;
@ -444,6 +454,13 @@ static int seg6_do_srh(struct sk_buff *skb)
return 0; 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, static int seg6_input_finish(struct net *net, struct sock *sk,
struct sk_buff *skb) struct sk_buff *skb)
{ {
@ -458,31 +475,33 @@ static int seg6_input_core(struct net *net, struct sock *sk,
struct seg6_lwt *slwt; struct seg6_lwt *slwt;
int err; int err;
err = seg6_do_srh(skb);
if (unlikely(err))
goto drop;
slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate); slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
local_bh_disable(); local_bh_disable();
dst = dst_cache_get(&slwt->cache); dst = dst_cache_get(&slwt->cache);
local_bh_enable();
err = seg6_do_srh(skb, dst);
if (unlikely(err))
goto drop;
if (!dst) { if (!dst) {
ip6_route_input(skb); ip6_route_input(skb);
dst = skb_dst(skb); dst = skb_dst(skb);
if (!dst->error) { if (!dst->error) {
local_bh_disable();
dst_cache_set_ip6(&slwt->cache, dst, dst_cache_set_ip6(&slwt->cache, dst,
&ipv6_hdr(skb)->saddr); &ipv6_hdr(skb)->saddr);
local_bh_enable();
} }
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
goto drop;
} else { } else {
skb_dst_drop(skb); skb_dst_drop(skb);
skb_dst_set(skb, dst); skb_dst_set(skb, dst);
} }
local_bh_enable();
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
goto drop;
if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled)) if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, 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; struct seg6_lwt *slwt;
int err; int err;
err = seg6_do_srh(skb);
if (unlikely(err))
goto drop;
slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate); slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
local_bh_disable(); local_bh_disable();
dst = dst_cache_get(&slwt->cache); dst = dst_cache_get(&slwt->cache);
local_bh_enable(); local_bh_enable();
err = seg6_do_srh(skb, dst);
if (unlikely(err))
goto drop;
if (unlikely(!dst)) { if (unlikely(!dst)) {
struct ipv6hdr *hdr = ipv6_hdr(skb); struct ipv6hdr *hdr = ipv6_hdr(skb);
struct flowi6 fl6; struct flowi6 fl6;
@ -559,15 +578,15 @@ static int seg6_output_core(struct net *net, struct sock *sk,
local_bh_disable(); local_bh_disable();
dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr); dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
local_bh_enable(); local_bh_enable();
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
goto drop;
} }
skb_dst_drop(skb); skb_dst_drop(skb);
skb_dst_set(skb, dst); skb_dst_set(skb, dst);
err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
if (unlikely(err))
goto drop;
if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled)) if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk, skb, return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk, skb,
NULL, skb_dst(skb)->dev, dst_output); NULL, skb_dst(skb)->dev, dst_output);