tcp: constify tcp_openreq_init_rwin()

Soon, listener socket wont be locked when tcp_openreq_init_rwin()
is called. We need to read socket fields once, as their value
could change under us.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index c006255..d37ad0c 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1207,7 +1207,8 @@ static inline int tcp_full_space(const struct sock *sk)
 }
 
 extern void tcp_openreq_init_rwin(struct request_sock *req,
-                                 struct sock *sk, struct dst_entry *dst);
+                                 const struct sock *sk_listener,
+                                 const struct dst_entry *dst);
 
 void tcp_enter_memory_pressure(struct sock *sk);
 

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 85830bb..e0a87c2 100644 (file)
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -362,27 +362,35 @@ void tcp_twsk_destructor(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
 
+/* Warning : This function is called without sk_listener being locked.
+ * Be sure to read socket fields once, as their value could change under us.
+ */
 void tcp_openreq_init_rwin(struct request_sock *req,
-                          struct sock *sk, struct dst_entry *dst)
+                          const struct sock *sk_listener,
+                          const struct dst_entry *dst)
 {
        struct inet_request_sock *ireq = inet_rsk(req);
-       struct tcp_sock *tp = tcp_sk(sk);
-       __u8 rcv_wscale;
+       const struct tcp_sock *tp = tcp_sk(sk_listener);
+       u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
+       int full_space = tcp_full_space(sk_listener);
        int mss = dst_metric_advmss(dst);
+       u32 window_clamp;
+       __u8 rcv_wscale;
 
-       if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
-               mss = tp->rx_opt.user_mss;
+       if (user_mss && user_mss < mss)
+               mss = user_mss;
 
+       window_clamp = READ_ONCE(tp->window_clamp);
        /* Set this up on the first call only */
-       req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
+       req->window_clamp = window_clamp ? : dst_metric(dst, RTAX_WINDOW);
 
        /* limit the window selection if the user enforce a smaller rx buffer */
-       if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
-           (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
-               req->window_clamp = tcp_full_space(sk);
+       if (sk_listener->sk_userlocks & SOCK_RCVBUF_LOCK &&
+           (req->window_clamp > full_space || req->window_clamp == 0))
+               req->window_clamp = full_space;
 
        /* tcp_full_space because it is guaranteed to be the first packet */
-       tcp_select_initial_window(tcp_full_space(sk),
+       tcp_select_initial_window(full_space,
                mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
                &req->rcv_wnd,
                &req->window_clamp,