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Date: Tue, 12 Sep 2023 16:02:11 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 13/14] ipv6: lockless IPV6_MTU_DISCOVER implementation
Most np->pmtudisc reads are racy.
Move this 3bit field on a full byte, add annotations
and make IPV6_MTU_DISCOVER setsockopt() lockless.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/linux/ipv6.h | 5 ++---
include/net/ip6_route.h | 14 +++++++++-----
net/ipv6/ip6_output.c | 4 ++--
net/ipv6/ipv6_sockglue.c | 17 ++++++++---------
net/ipv6/raw.c | 2 +-
net/ipv6/udp.c | 2 +-
net/netfilter/ipvs/ip_vs_sync.c | 2 +-
7 files changed, 24 insertions(+), 22 deletions(-)
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index f288a35f157f73ded445639c30f3365047fd9ddc..10f521a6a9c8a881b4677d53597929622ae95b67 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -243,13 +243,12 @@ struct ipv6_pinfo {
} rxopt;
/* sockopt flags */
- __u16 sndflow:1,
- pmtudisc:3,
- padding:1, /* 1 bit hole */
+ __u8 sndflow:1,
srcprefs:3; /* 001: prefer temporary address
* 010: prefer public address
* 100: prefer care-of address
*/
+ __u8 pmtudisc;
__u8 min_hopcount;
__u8 tclass;
__be32 rcv_flowinfo;
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index b32539bb0fb05c67b5849bb219be59fabe5bb51c..b1ea49900b4ae17cb3436f884e26f5ae3a7a761c 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -266,7 +266,7 @@ static inline unsigned int ip6_skb_dst_mtu(const struct sk_buff *skb)
const struct dst_entry *dst = skb_dst(skb);
unsigned int mtu;
- if (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) {
+ if (np && READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE) {
mtu = READ_ONCE(dst->dev->mtu);
mtu -= lwtunnel_headroom(dst->lwtstate, mtu);
} else {
@@ -277,14 +277,18 @@ static inline unsigned int ip6_skb_dst_mtu(const struct sk_buff *skb)
static inline bool ip6_sk_accept_pmtu(const struct sock *sk)
{
- return inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_INTERFACE &&
- inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_OMIT;
+ u8 pmtudisc = READ_ONCE(inet6_sk(sk)->pmtudisc);
+
+ return pmtudisc != IPV6_PMTUDISC_INTERFACE &&
+ pmtudisc != IPV6_PMTUDISC_OMIT;
}
static inline bool ip6_sk_ignore_df(const struct sock *sk)
{
- return inet6_sk(sk)->pmtudisc < IPV6_PMTUDISC_DO ||
- inet6_sk(sk)->pmtudisc == IPV6_PMTUDISC_OMIT;
+ u8 pmtudisc = READ_ONCE(inet6_sk(sk)->pmtudisc);
+
+ return pmtudisc < IPV6_PMTUDISC_DO ||
+ pmtudisc == IPV6_PMTUDISC_OMIT;
}
static inline const struct in6_addr *rt6_nexthop(const struct rt6_info *rt,
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index f87d8491d7e273f167b7b144a7e134783e1b80f6..7e5d9eeb990fd4549be753fdaaf1e6c6c21d3f8d 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1436,10 +1436,10 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
v6_cork->hop_limit = ipc6->hlimit;
v6_cork->tclass = ipc6->tclass;
if (rt->dst.flags & DST_XFRM_TUNNEL)
- mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?
+ mtu = READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE ?
READ_ONCE(rt->dst.dev->mtu) : dst_mtu(&rt->dst);
else
- mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?
+ mtu = READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE ?
READ_ONCE(rt->dst.dev->mtu) : dst_mtu(xfrm_dst_path(&rt->dst));
frag_size = READ_ONCE(np->frag_size);
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index c22a492e05360b68ef6868707e363f2ce84a4c35..85ea42644dcbbe3ed8f625e51ffc6d55ada40156 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -493,6 +493,13 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
return -EINVAL;
inet6_assign_bit(RTALERT_ISOLATE, sk, valbool);
return 0;
+ case IPV6_MTU_DISCOVER:
+ if (optlen < sizeof(int))
+ return -EINVAL;
+ if (val < IPV6_PMTUDISC_DONT || val > IPV6_PMTUDISC_OMIT)
+ return -EINVAL;
+ WRITE_ONCE(np->pmtudisc, val);
+ return 0;
}
if (needs_rtnl)
rtnl_lock();
@@ -941,14 +948,6 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
goto e_inval;
retv = ip6_ra_control(sk, val);
break;
- case IPV6_MTU_DISCOVER:
- if (optlen < sizeof(int))
- goto e_inval;
- if (val < IPV6_PMTUDISC_DONT || val > IPV6_PMTUDISC_OMIT)
- goto e_inval;
- np->pmtudisc = val;
- retv = 0;
- break;
case IPV6_FLOWINFO_SEND:
if (optlen < sizeof(int))
goto e_inval;
@@ -1374,7 +1373,7 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
break;
case IPV6_MTU_DISCOVER:
- val = np->pmtudisc;
+ val = READ_ONCE(np->pmtudisc);
break;
case IPV6_RECVERR:
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 71f6bdccfa1f39290e1b573ff8c647d91fd007a4..47372cceb98f6e606346b74230b03e76e303822c 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -307,7 +307,7 @@ static void rawv6_err(struct sock *sk, struct sk_buff *skb,
harderr = icmpv6_err_convert(type, code, &err);
if (type == ICMPV6_PKT_TOOBIG) {
ip6_sk_update_pmtu(skb, sk, info);
- harderr = (np->pmtudisc == IPV6_PMTUDISC_DO);
+ harderr = (READ_ONCE(np->pmtudisc) == IPV6_PMTUDISC_DO);
}
if (type == NDISC_REDIRECT) {
ip6_sk_redirect(skb, sk);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 65f6217d36cb7c862f1511a058a7a5973c40cef8..97fabbd7e7aa8bf66bfe21a98f97d4408af13d2b 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -598,7 +598,7 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
if (!ip6_sk_accept_pmtu(sk))
goto out;
ip6_sk_update_pmtu(skb, sk, info);
- if (np->pmtudisc != IPV6_PMTUDISC_DONT)
+ if (READ_ONCE(np->pmtudisc) != IPV6_PMTUDISC_DONT)
harderr = 1;
}
if (type == NDISC_REDIRECT) {
diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
index df1b33b61059eef1e86baefc63e138108a50a081..5820a8156c4701bb163f569d735c389d7a8e3820 100644
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -1341,7 +1341,7 @@ static void set_mcast_pmtudisc(struct sock *sk, int val)
struct ipv6_pinfo *np = inet6_sk(sk);
/* IPV6_MTU_DISCOVER */
- np->pmtudisc = val;
+ WRITE_ONCE(np->pmtudisc, val);
}
#endif
release_sock(sk);
--
2.42.0.283.g2d96d420d3-goog
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