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Message-ID: <1335348157.3274.30.camel@edumazet-glaptop>
Date: Wed, 25 Apr 2012 12:02:37 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Tore Anderson <tore@....no>
Cc: Maciej Żenczykowski <maze@...gle.com>,
David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCH net-next] ipv6: RTAX_FEATURE_ALLFRAG causes inefficient
TCP segment sizing
On Wed, 2012-04-25 at 11:38 +0200, Eric Dumazet wrote:
> Hmm, but what if we change linux to choice a) instead of b) ?
>
> That is, not cap mtu to minimum value 1280 (and not use anymore
> RTAX_FEATURE_ALLFRAG) : dst_allfrag() would be always false.
>
> In this case, do we still need to send the frag header ?
>
> I ask this because some TSO6 implementations probably dont cope very
> well with this added header (untested path)
>
So a patch against net-next would looks like :
(Incredible, we remove some code in linux ;) )
include/linux/rtnetlink.h | 2 +-
include/net/dst.h | 7 -------
include/net/inet_sock.h | 2 +-
net/ipv6/ip6_output.c | 14 +++++---------
net/ipv6/route.c | 28 ----------------------------
net/ipv6/xfrm6_output.c | 9 ++++-----
6 files changed, 11 insertions(+), 51 deletions(-)
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 2c1de89..92ed273 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -380,7 +380,7 @@ enum {
#define RTAX_FEATURE_ECN 0x00000001
#define RTAX_FEATURE_SACK 0x00000002
#define RTAX_FEATURE_TIMESTAMP 0x00000004
-#define RTAX_FEATURE_ALLFRAG 0x00000008
+#define RTAX_FEATURE_ALLFRAG 0x00000008 /* not used anymore */
struct rta_session {
__u8 proto;
diff --git a/include/net/dst.h b/include/net/dst.h
index ff4da42..e69c55b 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -226,13 +226,6 @@ static inline void set_dst_metric_rtt(struct dst_entry *dst, int metric,
dst_metric_set(dst, metric, jiffies_to_msecs(rtt));
}
-static inline u32
-dst_allfrag(const struct dst_entry *dst)
-{
- int ret = dst_feature(dst, RTAX_FEATURE_ALLFRAG);
- return ret;
-}
-
static inline int
dst_metric_locked(const struct dst_entry *dst, int metric)
{
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index ae17e13..381ddc3 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -177,7 +177,7 @@ struct inet_sock {
};
#define IPCORK_OPT 1 /* ip-options has been held in ipcork.opt */
-#define IPCORK_ALLFRAG 2 /* always fragment (for ipv6 for now) */
+#define IPCORK_ALLFRAG 2 /* always fragment (for ipv6 for now), unused */
static inline struct inet_sock *inet_sk(const struct sock *sk)
{
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index b7ca461..314275e 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -152,11 +152,10 @@ static int ip6_finish_output2(struct sk_buff *skb)
static int ip6_finish_output(struct sk_buff *skb)
{
- if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
- dst_allfrag(skb_dst(skb)))
+ if (skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb))
return ip6_fragment(skb, ip6_finish_output2);
- else
- return ip6_finish_output2(skb);
+
+ return ip6_finish_output2(skb);
}
int ip6_output(struct sk_buff *skb)
@@ -1255,8 +1254,6 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
mtu = np->frag_size;
}
cork->fragsize = mtu;
- if (dst_allfrag(rt->dst.path))
- cork->flags |= IPCORK_ALLFRAG;
cork->length = 0;
sk->sk_sndmsg_page = NULL;
sk->sk_sndmsg_off = 0;
@@ -1335,7 +1332,7 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
while (length > 0) {
/* Check if the remaining data fits into current packet. */
- copy = (cork->length <= mtu && !(cork->flags & IPCORK_ALLFRAG) ? mtu : maxfraglen) - skb->len;
+ copy = (cork->length <= mtu ? mtu : maxfraglen) - skb->len;
if (copy < length)
copy = maxfraglen - skb->len;
@@ -1360,7 +1357,7 @@ alloc_new_skb:
* we know we need more fragment(s).
*/
datalen = length + fraggap;
- if (datalen > (cork->length <= mtu && !(cork->flags & IPCORK_ALLFRAG) ? mtu : maxfraglen) - fragheaderlen)
+ if (datalen > (cork->length <= mtu ? mtu : maxfraglen) - fragheaderlen)
datalen = maxfraglen - fragheaderlen;
fraglen = datalen + fragheaderlen;
@@ -1550,7 +1547,6 @@ static void ip6_cork_release(struct inet_sock *inet, struct ipv6_pinfo *np)
if (inet->cork.base.dst) {
dst_release(inet->cork.base.dst);
inet->cork.base.dst = NULL;
- inet->cork.base.flags &= ~IPCORK_ALLFRAG;
}
memset(&inet->cork.fl, 0, sizeof(inet->cork.fl));
}
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 0aefc36..43e2ec1 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1044,12 +1044,6 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
if (mtu < dst_mtu(dst) && rt6->rt6i_dst.plen == 128) {
rt6->rt6i_flags |= RTF_MODIFIED;
- if (mtu < IPV6_MIN_MTU) {
- u32 features = dst_metric(dst, RTAX_FEATURES);
- mtu = IPV6_MIN_MTU;
- features |= RTAX_FEATURE_ALLFRAG;
- dst_metric_set(dst, RTAX_FEATURES, features);
- }
dst_metric_set(dst, RTAX_MTU, mtu);
}
}
@@ -1707,7 +1701,6 @@ static void rt6_do_pmtu_disc(const struct in6_addr *daddr, const struct in6_addr
struct net *net, u32 pmtu, int ifindex)
{
struct rt6_info *rt, *nrt;
- int allfrag = 0;
again:
rt = rt6_lookup(net, daddr, saddr, ifindex, 0);
if (!rt)
@@ -1721,17 +1714,6 @@ again:
if (pmtu >= dst_mtu(&rt->dst))
goto out;
- if (pmtu < IPV6_MIN_MTU) {
- /*
- * According to RFC2460, PMTU is set to the IPv6 Minimum Link
- * MTU (1280) and a fragment header should always be included
- * after a node receiving Too Big message reporting PMTU is
- * less than the IPv6 Minimum Link MTU.
- */
- pmtu = IPV6_MIN_MTU;
- allfrag = 1;
- }
-
/* New mtu received -> path was valid.
They are sent only in response to data packets,
so that this nexthop apparently is reachable. --ANK
@@ -1745,11 +1727,6 @@ again:
*/
if (rt->rt6i_flags & RTF_CACHE) {
dst_metric_set(&rt->dst, RTAX_MTU, pmtu);
- if (allfrag) {
- u32 features = dst_metric(&rt->dst, RTAX_FEATURES);
- features |= RTAX_FEATURE_ALLFRAG;
- dst_metric_set(&rt->dst, RTAX_FEATURES, features);
- }
rt6_update_expires(rt, net->ipv6.sysctl.ip6_rt_mtu_expires);
rt->rt6i_flags |= RTF_MODIFIED;
goto out;
@@ -1767,11 +1744,6 @@ again:
if (nrt) {
dst_metric_set(&nrt->dst, RTAX_MTU, pmtu);
- if (allfrag) {
- u32 features = dst_metric(&nrt->dst, RTAX_FEATURES);
- features |= RTAX_FEATURE_ALLFRAG;
- dst_metric_set(&nrt->dst, RTAX_FEATURES, features);
- }
/* According to RFC 1981, detecting PMTU increase shouldn't be
* happened within 5 mins, the recommended timer is 10 mins.
diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index 8755a30..8242af0 100644
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -146,11 +146,10 @@ static int __xfrm6_output(struct sk_buff *skb)
return -EMSGSIZE;
}
- if (x->props.mode == XFRM_MODE_TUNNEL &&
- ((skb->len > mtu && !skb_is_gso(skb)) ||
- dst_allfrag(skb_dst(skb)))) {
- return ip6_fragment(skb, x->outer_mode->afinfo->output_finish);
- }
+ if (x->props.mode == XFRM_MODE_TUNNEL && skb->len > mtu &&
+ !skb_is_gso(skb))
+ return ip6_fragment(skb, x->outer_mode->afinfo->output_finish);
+
return x->outer_mode->afinfo->output_finish(skb);
}
--
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