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Message-ID: <20250828195823.3958522-6-edumazet@google.com>
Date: Thu, 28 Aug 2025 19:58:20 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Neal Cardwell <ncardwell@...gle.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>,
David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 5/8] net: use dst_dev_rcu() in sk_setup_caps()
Use RCU to protect accesses to dst->dev from sk_setup_caps()
and sk_dst_gso_max_size().
Also use dst_dev_rcu() in ip6_dst_mtu_maybe_forward(),
and ip_dst_mtu_maybe_forward().
ip4_dst_hoplimit() can use dst_dev_net_rcu().
Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/ip.h | 6 ++++--
include/net/ip6_route.h | 2 +-
include/net/route.h | 2 +-
net/core/sock.c | 16 ++++++++++------
4 files changed, 16 insertions(+), 10 deletions(-)
diff --git a/include/net/ip.h b/include/net/ip.h
index befcba575129ac436912d9c19740a0a72fe23954..6dbd2bf8fa9c96dc342acc171471704981123eec 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -467,12 +467,14 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
bool forwarding)
{
const struct rtable *rt = dst_rtable(dst);
+ const struct net_device *dev;
unsigned int mtu, res;
struct net *net;
rcu_read_lock();
- net = dev_net_rcu(dst_dev(dst));
+ dev = dst_dev_rcu(dst);
+ net = dev_net_rcu(dev);
if (READ_ONCE(net->ipv4.sysctl_ip_fwd_use_pmtu) ||
ip_mtu_locked(dst) ||
!forwarding) {
@@ -486,7 +488,7 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
if (mtu)
goto out;
- mtu = READ_ONCE(dst_dev(dst)->mtu);
+ mtu = READ_ONCE(dev->mtu);
if (unlikely(ip_mtu_locked(dst))) {
if (rt->rt_uses_gateway && mtu > 576)
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 9255f21818ee7b03d2608fd399b082c0098c7028..59f48ca3abdf5a8aef6b4ece13f9a1774fc04f38 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -337,7 +337,7 @@ static inline unsigned int ip6_dst_mtu_maybe_forward(const struct dst_entry *dst
mtu = IPV6_MIN_MTU;
rcu_read_lock();
- idev = __in6_dev_get(dst_dev(dst));
+ idev = __in6_dev_get(dst_dev_rcu(dst));
if (idev)
mtu = READ_ONCE(idev->cnf.mtu6);
rcu_read_unlock();
diff --git a/include/net/route.h b/include/net/route.h
index c71998f464f8e6f2e4e3d03bd0db6d0da875f636..f90106f383c56d5cdaa8d455c840dbcf9a5e9555 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -390,7 +390,7 @@ static inline int ip4_dst_hoplimit(const struct dst_entry *dst)
const struct net *net;
rcu_read_lock();
- net = dev_net_rcu(dst_dev(dst));
+ net = dst_dev_net_rcu(dst);
hoplimit = READ_ONCE(net->ipv4.sysctl_ip_default_ttl);
rcu_read_unlock();
}
diff --git a/net/core/sock.c b/net/core/sock.c
index e66ad1ec3a2d969b71835a492806563519459749..9a8290fcc35d66b2011157a30c13653784e78e96 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2587,7 +2587,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
}
EXPORT_SYMBOL_GPL(sk_clone_lock);
-static u32 sk_dst_gso_max_size(struct sock *sk, struct dst_entry *dst)
+static u32 sk_dst_gso_max_size(struct sock *sk, const struct net_device *dev)
{
bool is_ipv6 = false;
u32 max_size;
@@ -2597,8 +2597,8 @@ static u32 sk_dst_gso_max_size(struct sock *sk, struct dst_entry *dst)
!ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr));
#endif
/* pairs with the WRITE_ONCE() in netif_set_gso(_ipv4)_max_size() */
- max_size = is_ipv6 ? READ_ONCE(dst_dev(dst)->gso_max_size) :
- READ_ONCE(dst_dev(dst)->gso_ipv4_max_size);
+ max_size = is_ipv6 ? READ_ONCE(dev->gso_max_size) :
+ READ_ONCE(dev->gso_ipv4_max_size);
if (max_size > GSO_LEGACY_MAX_SIZE && !sk_is_tcp(sk))
max_size = GSO_LEGACY_MAX_SIZE;
@@ -2607,9 +2607,12 @@ static u32 sk_dst_gso_max_size(struct sock *sk, struct dst_entry *dst)
void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
{
+ const struct net_device *dev;
u32 max_segs = 1;
- sk->sk_route_caps = dst_dev(dst)->features;
+ rcu_read_lock();
+ dev = dst_dev_rcu(dst);
+ sk->sk_route_caps = dev->features;
if (sk_is_tcp(sk)) {
struct inet_connection_sock *icsk = inet_csk(sk);
@@ -2625,13 +2628,14 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
} else {
sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM;
- sk->sk_gso_max_size = sk_dst_gso_max_size(sk, dst);
+ sk->sk_gso_max_size = sk_dst_gso_max_size(sk, dev);
/* pairs with the WRITE_ONCE() in netif_set_gso_max_segs() */
- max_segs = max_t(u32, READ_ONCE(dst_dev(dst)->gso_max_segs), 1);
+ max_segs = max_t(u32, READ_ONCE(dev->gso_max_segs), 1);
}
}
sk->sk_gso_max_segs = max_segs;
sk_dst_set(sk, dst);
+ rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(sk_setup_caps);
--
2.51.0.318.gd7df087d1a-goog
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