tcp: Fix -Wc23-extensions in tcp_options_write()

Clang warns (or errors with CONFIG_WERROR=y) when CONFIG_TCP_AO is set:

  net/ipv4/tcp_output.c:663:2: error: label at end of compound statement is a C23 extension [-Werror,-Wc23-extensions]
    663 |         }
        |         ^
  1 error generated.

On earlier releases (such as clang-11, the current minimum supported
version for building the kernel) that do not support C23, this was a
hard error unconditionally:

  net/ipv4/tcp_output.c:663:2: error: expected statement
          }
          ^
  1 error generated.

While adding a semicolon after the label would resolve this, it is more
in line with the kernel as a whole to refactor this block into a
standalone function, which means the goto a label construct can just be
replaced with a return statement. Do so to resolve the warning.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1953
Fixes: 1e03d32bea8e ("net/tcp: Add TCP-AO sign to outgoing packets")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Dmitry Safonov <dima@arista.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 0d8dd5b7e2e5e078d3e4bcc0d4270215f1be366d..eb13a55d660c2376968f11ee3265280f8cc9e1bd 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -601,6 +601,44 @@ static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
 }
 #endif
 
+static __be32 *process_tcp_ao_options(struct tcp_sock *tp,
+                                     const struct tcp_request_sock *tcprsk,
+                                     struct tcp_out_options *opts,
+                                     struct tcp_key *key, __be32 *ptr)
+{
+#ifdef CONFIG_TCP_AO
+       u8 maclen = tcp_ao_maclen(key->ao_key);
+
+       if (tcprsk) {
+               u8 aolen = maclen + sizeof(struct tcp_ao_hdr);
+
+               *ptr++ = htonl((TCPOPT_AO << 24) | (aolen << 16) |
+                              (tcprsk->ao_keyid << 8) |
+                              (tcprsk->ao_rcv_next));
+       } else {
+               struct tcp_ao_key *rnext_key;
+               struct tcp_ao_info *ao_info;
+
+               ao_info = rcu_dereference_check(tp->ao_info,
+                       lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk));
+               rnext_key = READ_ONCE(ao_info->rnext_key);
+               if (WARN_ON_ONCE(!rnext_key))
+                       return ptr;
+               *ptr++ = htonl((TCPOPT_AO << 24) |
+                              (tcp_ao_len(key->ao_key) << 16) |
+                              (key->ao_key->sndid << 8) |
+                              (rnext_key->rcvid));
+       }
+       opts->hash_location = (__u8 *)ptr;
+       ptr += maclen / sizeof(*ptr);
+       if (unlikely(maclen % sizeof(*ptr))) {
+               memset(ptr, TCPOPT_NOP, sizeof(*ptr));
+               ptr++;
+       }
+#endif
+       return ptr;
+}
+
 /* Write previously computed TCP options to the packet.
  *
  * Beware: Something in the Internet is very sensitive to the ordering of
@@ -629,37 +667,7 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
                opts->hash_location = (__u8 *)ptr;
                ptr += 4;
        } else if (tcp_key_is_ao(key)) {
-#ifdef CONFIG_TCP_AO
-               u8 maclen = tcp_ao_maclen(key->ao_key);
-
-               if (tcprsk) {
-                       u8 aolen = maclen + sizeof(struct tcp_ao_hdr);
-
-                       *ptr++ = htonl((TCPOPT_AO << 24) | (aolen << 16) |
-                                      (tcprsk->ao_keyid << 8) |
-                                      (tcprsk->ao_rcv_next));
-               } else {
-                       struct tcp_ao_key *rnext_key;
-                       struct tcp_ao_info *ao_info;
-
-                       ao_info = rcu_dereference_check(tp->ao_info,
-                               lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk));
-                       rnext_key = READ_ONCE(ao_info->rnext_key);
-                       if (WARN_ON_ONCE(!rnext_key))
-                               goto out_ao;
-                       *ptr++ = htonl((TCPOPT_AO << 24) |
-                                      (tcp_ao_len(key->ao_key) << 16) |
-                                      (key->ao_key->sndid << 8) |
-                                      (rnext_key->rcvid));
-               }
-               opts->hash_location = (__u8 *)ptr;
-               ptr += maclen / sizeof(*ptr);
-               if (unlikely(maclen % sizeof(*ptr))) {
-                       memset(ptr, TCPOPT_NOP, sizeof(*ptr));
-                       ptr++;
-               }
-out_ao:
-#endif
+               ptr = process_tcp_ao_options(tp, tcprsk, opts, key, ptr);
        }
        if (unlikely(opts->mss)) {
                *ptr++ = htonl((TCPOPT_MSS << 24) |