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 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:
- 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: Justin Iurman <justin.iurman@uliege.be>
---
net/ipv6/ioam6_iptunnel.c | 82 +++++++++++++++++++--------------------
1 file changed, 41 insertions(+), 41 deletions(-)
diff --git a/net/ipv6/ioam6_iptunnel.c b/net/ipv6/ioam6_iptunnel.c
index 9d8422e350f8..2b9f3cb29db7 100644
--- a/net/ipv6/ioam6_iptunnel.c
+++ b/net/ipv6/ioam6_iptunnel.c
@@ -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 *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(dst, skb));
if (unlikely(err))
return err;
@@ -291,16 +292,16 @@ 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 *dst)
{
- struct dst_entry *dst = skb_dst(skb);
struct ipv6hdr *hdr, *inner_hdr;
int hdrlen, len, err;
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(dst, skb));
if (unlikely(err))
return err;
@@ -324,7 +325,7 @@ static int ioam6_do_encap(struct net *net, struct sk_buff *skb,
if (has_tunsrc)
memcpy(&hdr->saddr, tunsrc, sizeof(*tunsrc));
else
- ipv6_dev_get_saddr(net, dst->dev, &hdr->daddr,
+ ipv6_dev_get_saddr(net, skb_dst(skb)->dev, &hdr->daddr,
IPV6_PREFER_SRC_PUBLIC, &hdr->saddr);
skb_postpush_rcsum(skb, hdr, len);
@@ -334,7 +335,7 @@ 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, *orig_dst = skb_dst(skb);
struct in6_addr orig_daddr;
struct ioam6_lwt *ilwt;
int err = -EINVAL;
@@ -343,7 +344,7 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
if (skb->protocol != htons(ETH_P_IPV6))
goto drop;
- ilwt = ioam6_lwt_state(dst->lwtstate);
+ ilwt = ioam6_lwt_state(orig_dst->lwtstate);
/* Check for insertion frequency (i.e., "k over n" insertions) */
pkt_cnt = atomic_fetch_inc(&ilwt->pkt_cnt);
@@ -352,6 +353,10 @@ static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
orig_daddr = ipv6_hdr(skb)->daddr;
+ local_bh_disable();
+ dst = dst_cache_get(&ilwt->cache);
+ local_bh_enable();
+
switch (ilwt->mode) {
case IOAM6_IPTUNNEL_MODE_INLINE:
do_inline:
@@ -359,7 +364,7 @@ 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, dst);
if (unlikely(err))
goto drop;
@@ -369,7 +374,7 @@ 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, dst);
if (unlikely(err))
goto drop;
@@ -387,45 +392,40 @@ 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 (unlikely(!dst)) {
+ struct ipv6hdr *hdr = ipv6_hdr(skb);
+ struct flowi6 fl6;
+
+ memset(&fl6, 0, sizeof(fl6));
+ fl6.daddr = hdr->daddr;
+ fl6.saddr = hdr->saddr;
+ fl6.flowlabel = ip6_flowinfo(hdr);
+ 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);
+ goto drop;
+ }
- if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {
local_bh_disable();
- dst = dst_cache_get(&ilwt->cache);
+ dst_cache_set_ip6(&ilwt->cache, dst, &fl6.saddr);
local_bh_enable();
- if (unlikely(!dst)) {
- struct ipv6hdr *hdr = ipv6_hdr(skb);
- struct flowi6 fl6;
-
- memset(&fl6, 0, sizeof(fl6));
- fl6.daddr = hdr->daddr;
- fl6.saddr = hdr->saddr;
- fl6.flowlabel = ip6_flowinfo(hdr);
- 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);
- goto drop;
- }
-
- local_bh_disable();
- dst_cache_set_ip6(&ilwt->cache, dst, &fl6.saddr);
- local_bh_enable();
- }
+ err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
+ if (unlikely(err))
+ goto drop;
+ }
- skb_dst_drop(skb);
- skb_dst_set(skb, dst);
+ skb_dst_drop(skb);
+ skb_dst_set(skb, dst);
+ if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr))
return dst_output(net, sk, skb);
- }
out:
- return dst->lwtstate->orig_output(net, sk, skb);
+ return orig_dst->lwtstate->orig_output(net, sk, skb);
drop:
kfree_skb(skb);
return err;
--
2.34.1On 11/18/24 14:15, Justin Iurman wrote:
> @@ -387,45 +392,40 @@ 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 (unlikely(!dst)) {
> + struct ipv6hdr *hdr = ipv6_hdr(skb);
> + struct flowi6 fl6;
> +
> + memset(&fl6, 0, sizeof(fl6));
> + fl6.daddr = hdr->daddr;
> + fl6.saddr = hdr->saddr;
> + fl6.flowlabel = ip6_flowinfo(hdr);
> + 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);
> + goto drop;
> + }
>
> - if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {
> local_bh_disable();
> - dst = dst_cache_get(&ilwt->cache);
> + dst_cache_set_ip6(&ilwt->cache, dst, &fl6.saddr);
> local_bh_enable();
>
> - if (unlikely(!dst)) {
> - struct ipv6hdr *hdr = ipv6_hdr(skb);
> - struct flowi6 fl6;
> -
> - memset(&fl6, 0, sizeof(fl6));
> - fl6.daddr = hdr->daddr;
> - fl6.saddr = hdr->saddr;
> - fl6.flowlabel = ip6_flowinfo(hdr);
> - 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);
> - goto drop;
> - }
> -
> - local_bh_disable();
> - dst_cache_set_ip6(&ilwt->cache, dst, &fl6.saddr);
> - local_bh_enable();
> - }
> + err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
> + if (unlikely(err))
> + goto drop;
> + }
>
> - skb_dst_drop(skb);
> - skb_dst_set(skb, dst);
> + skb_dst_drop(skb);
> + skb_dst_set(skb, dst);
Why the above 2 statements are not done only in case of ip address
match, as in the existing code?
>
> + if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr))
> return dst_output(net, sk, skb);
> - }
Thanks,
Paolo
On 11/19/24 11:42, Paolo Abeni wrote>> - skb_dst_drop(skb);
>> - skb_dst_set(skb, dst);
>> + skb_dst_drop(skb);
>> + skb_dst_set(skb, dst);
>
> Why the above 2 statements are not done only in case of ip address
> match, as in the existing code?
I guess you meant "when they do *not* match", right?
>>
>> + if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr))
>> return dst_output(net, sk, skb);
>> - }
Good catch. Initially, the only reason was to be on the safe side. Will
change it to:
if (!ipv6_addr_equal(&orig_daddr, &ipv6_hdr(skb)->daddr)) {
skb_dst_drop(skb);
skb_dst_set(skb, dst);
return dst_output(net, sk, skb);
}
Thanks Paolo!
Cheers,
Justin
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