From d57f4b874946e997be52f5ebb5e0e1dad368c16f Mon Sep 17 00:00:00 2001 From: Jakub Sitnicki Date: Wed, 17 Sep 2025 15:22:04 +0200 Subject: tcp: Update bind bucket state on port release Today, once an inet_bind_bucket enters a state where fastreuse >= 0 or fastreuseport >= 0 after a socket is explicitly bound to a port, it remains in that state until all sockets are removed and the bucket is destroyed. In this state, the bucket is skipped during ephemeral port selection in connect(). For applications using a reduced ephemeral port range (IP_LOCAL_PORT_RANGE socket option), this can cause faster port exhaustion since blocked buckets are excluded from reuse. The reason the bucket state isn't updated on port release is unclear. Possibly a performance trade-off to avoid scanning bucket owners, or just an oversight. Fix it by recalculating the bucket state when a socket releases a port. To limit overhead, each inet_bind2_bucket stores its own (fastreuse, fastreuseport) state. On port release, only the relevant port-addr bucket is scanned, and the overall state is derived from these. Signed-off-by: Jakub Sitnicki Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250917-update-bind-bucket-state-on-unhash-v5-1-57168b661b47@cloudflare.com Signed-off-by: Paolo Abeni --- include/net/inet_connection_sock.h | 5 +++-- include/net/inet_hashtables.h | 2 ++ include/net/inet_timewait_sock.h | 3 ++- include/net/sock.h | 4 ++++ 4 files changed, 11 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index 0737d8e178dd..b4b886647607 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -316,8 +316,9 @@ int inet_csk_listen_start(struct sock *sk); void inet_csk_listen_stop(struct sock *sk); /* update the fast reuse flag when adding a socket */ -void inet_csk_update_fastreuse(struct inet_bind_bucket *tb, - struct sock *sk); +void inet_csk_update_fastreuse(const struct sock *sk, + struct inet_bind_bucket *tb, + struct inet_bind2_bucket *tb2); struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu); diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h index b787be651ce7..ac05a52d9e13 100644 --- a/include/net/inet_hashtables.h +++ b/include/net/inet_hashtables.h @@ -108,6 +108,8 @@ struct inet_bind2_bucket { struct hlist_node bhash_node; /* List of sockets hashed to this bucket */ struct hlist_head owners; + signed char fastreuse; + signed char fastreuseport; }; static inline struct net *ib_net(const struct inet_bind_bucket *ib) diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h index 3a31c74c9e15..63a644ff30de 100644 --- a/include/net/inet_timewait_sock.h +++ b/include/net/inet_timewait_sock.h @@ -70,7 +70,8 @@ struct inet_timewait_sock { unsigned int tw_transparent : 1, tw_flowlabel : 20, tw_usec_ts : 1, - tw_pad : 2, /* 2 bits hole */ + tw_connect_bind : 1, + tw_pad : 1, /* 1 bit hole */ tw_tos : 8; u32 tw_txhash; u32 tw_priority; diff --git a/include/net/sock.h b/include/net/sock.h index b4fefeea0213..8c5b64f41ab7 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1494,6 +1494,10 @@ static inline int __sk_prot_rehash(struct sock *sk) #define SOCK_BINDADDR_LOCK 4 #define SOCK_BINDPORT_LOCK 8 +/** + * define SOCK_CONNECT_BIND - &sock->sk_userlocks flag for auto-bind at connect() time + */ +#define SOCK_CONNECT_BIND 16 struct socket_alloc { struct socket socket; -- cgit v1.2.3