net: pass back whether socket was empty post accept

This adds an 'is_empty' argument to struct proto_accept_arg, which can be used to pass back information on whether or not the given socket has more connections to accept post the one just accepted. To utilize this information, the caller should initialize the 'is_empty' field to, eg, -1 and then check for 0/1 after the accept. If the field has been set, the caller knows whether there are more pending connections or not. If the field remains -1 after the accept call, the protocol doesn't support passing back this information. This patch wires it up for ipv4/6 TCP. Acked-by: Jakub Kicinski <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
torvalds · May 14, 2024 · 7951e36 · 7951e36
1 parent 0645fbe
commit 7951e36
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diff --git a/include/net/sock.h b/include/net/sock.h
@@ -1197,6 +1197,7 @@ static inline void sk_prot_clear_nulls(struct sock *sk, int size)
 struct proto_accept_arg {
  int flags;
  int err;
+ int is_empty;
  bool kern;
 };
 

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
@@ -692,6 +692,7 @@ struct sock *inet_csk_accept(struct sock *sk, struct proto_accept_arg *arg)
  goto out_err;
  }
  req = reqsk_queue_remove(queue, sk);
+ arg->is_empty = reqsk_queue_empty(queue);
  newsk = req->sk;
 
  if (sk->sk_protocol == IPPROTO_TCP &&