net: remove addr_len argument of recvmsg() handlers

Use msg->msg_namelen as a place holder instead of a
temporary variable, notably in inet[6]_recvmsg().

This removes stack canaries and allows tail-calls.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux
add/remove: 0/0 grow/shrink: 2/19 up/down: 26/-532 (-506)
Function                                     old     new   delta
rawv6_recvmsg                                744     767     +23
vsock_dgram_recvmsg                           55      58      +3
vsock_connectible_recvmsg                     50      47      -3
unix_stream_recvmsg                          161     158      -3
unix_seqpacket_recvmsg                        62      59      -3
unix_dgram_recvmsg                            42      39      -3
tcp_recvmsg                                  546     543      -3
mptcp_recvmsg                               1568    1565      -3
ping_recvmsg                                 806     800      -6
tcp_bpf_recvmsg_parser                       983     974      -9
ip_recv_error                                588     576     -12
ipv6_recv_rxpmtu                             442     428     -14
udp_recvmsg                                 1243    1224     -19
ipv6_recv_error                             1046    1024     -22
udpv6_recvmsg                               1487    1461     -26
raw_recvmsg                                  465     437     -28
udp_bpf_recvmsg                             1027     984     -43
sock_common_recvmsg                          103      27     -76
inet_recvmsg                                 257     175     -82
inet6_recvmsg                                257     175     -82
tcp_bpf_recvmsg                              663     568     -95
Total: Before=25143834, After=25143328, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260227151120.1346573-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

6 files changed, 18 insertions, 26 deletions

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 23cc9b4cb2f1..0b995a961359 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -661,25 +661,20 @@ int inet6_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 }
 
 INDIRECT_CALLABLE_DECLARE(int udpv6_recvmsg(struct sock *, struct msghdr *,
-					    size_t, int, int *));
+					    size_t, int));
 int inet6_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
 		  int flags)
 {
 	struct sock *sk = sock->sk;
 	const struct proto *prot;
-	int addr_len = 0;
-	int err;
 
 	if (likely(!(flags & MSG_ERRQUEUE)))
 		sock_rps_record_flow(sk);
 
 	/* IPV6_ADDRFORM can change sk->sk_prot under us. */
 	prot = READ_ONCE(sk->sk_prot);
-	err = INDIRECT_CALL_2(prot->recvmsg, tcp_recvmsg, udpv6_recvmsg,
-			      sk, msg, size, flags, &addr_len);
-	if (err >= 0)
-		msg->msg_namelen = addr_len;
-	return err;
+	return INDIRECT_CALL_2(prot->recvmsg, tcp_recvmsg, udpv6_recvmsg,
+			       sk, msg, size, flags);
 }
 
 const struct proto_ops inet6_stream_ops = {
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index c564b68a0562..3cb84022a461 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -452,7 +452,7 @@ static bool ip6_datagram_support_cmsg(struct sk_buff *skb,
 /*
  *	Handle MSG_ERRQUEUE
  */
-int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
+int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sock_exterr_skb *serr;
@@ -503,7 +503,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 					       &sin->sin6_addr);
 			sin->sin6_scope_id = 0;
 		}
-		*addr_len = sizeof(*sin);
+		msg->msg_namelen = sizeof(*sin);
 	}
 
 	memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));
@@ -545,8 +545,7 @@ EXPORT_SYMBOL_GPL(ipv6_recv_error);
 /*
  *	Handle IPV6_RECVPATHMTU
  */
-int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len,
-		     int *addr_len)
+int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct sk_buff *skb;
@@ -579,7 +578,7 @@ int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len,
 		sin->sin6_port = 0;
 		sin->sin6_scope_id = mtu_info.ip6m_addr.sin6_scope_id;
 		sin->sin6_addr = mtu_info.ip6m_addr.sin6_addr;
-		*addr_len = sizeof(*sin);
+		msg->msg_namelen = sizeof(*sin);
 	}
 
 	put_cmsg(msg, SOL_IPV6, IPV6_PATHMTU, sizeof(mtu_info), &mtu_info);
diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index e4afc651731a..6e90d0bf9f3d 100644
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c
@@ -24,8 +24,7 @@
 #include <net/ping.h>
 
 /* Compatibility glue so we can support IPv6 when it's compiled as a module */
-static int dummy_ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len,
-				 int *addr_len)
+static int dummy_ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len)
 {
 	return -EAFNOSUPPORT;
 }
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 27a268059168..0ac704691100 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -432,7 +432,7 @@ int rawv6_rcv(struct sock *sk, struct sk_buff *skb)
  */
 
 static int rawv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
-			 int flags, int *addr_len)
+			 int flags)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
@@ -444,10 +444,10 @@ static int rawv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 		return -EOPNOTSUPP;
 
 	if (flags & MSG_ERRQUEUE)
-		return ipv6_recv_error(sk, msg, len, addr_len);
+		return ipv6_recv_error(sk, msg, len);
 
 	if (np->rxopt.bits.rxpmtu && READ_ONCE(np->rxpmtu))
-		return ipv6_recv_rxpmtu(sk, msg, len, addr_len);
+		return ipv6_recv_rxpmtu(sk, msg, len);
 
 	skb = skb_recv_datagram(sk, flags, &err);
 	if (!skb)
@@ -481,7 +481,7 @@ static int rawv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 		sin6->sin6_flowinfo = 0;
 		sin6->sin6_scope_id = ipv6_iface_scope_id(&sin6->sin6_addr,
 							  inet6_iif(skb));
-		*addr_len = sizeof(*sin6);
+		msg->msg_namelen = sizeof(*sin6);
 	}
 
 	sock_recv_cmsgs(msg, sk, skb);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 48f73401adf4..5a3984e59c90 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -465,7 +465,7 @@ static int udp6_skb_len(struct sk_buff *skb)
  */
 
 int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
-		  int flags, int *addr_len)
+		  int flags)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct inet_sock *inet = inet_sk(sk);
@@ -478,10 +478,10 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	int is_udp4;
 
 	if (flags & MSG_ERRQUEUE)
-		return ipv6_recv_error(sk, msg, len, addr_len);
+		return ipv6_recv_error(sk, msg, len);
 
 	if (np->rxopt.bits.rxpmtu && READ_ONCE(np->rxpmtu))
-		return ipv6_recv_rxpmtu(sk, msg, len, addr_len);
+		return ipv6_recv_rxpmtu(sk, msg, len);
 
 try_again:
 	off = sk_peek_offset(sk, flags);
@@ -553,11 +553,11 @@ try_again:
 				ipv6_iface_scope_id(&sin6->sin6_addr,
 						    inet6_iif(skb));
 		}
-		*addr_len = sizeof(*sin6);
+		msg->msg_namelen = sizeof(*sin6);
 
 		BPF_CGROUP_RUN_PROG_UDP6_RECVMSG_LOCK(sk,
 						      (struct sockaddr *)sin6,
-						      addr_len);
+						      &msg->msg_namelen);
 	}
 
 	if (udp_test_bit(GRO_ENABLED, sk))
diff --git a/net/ipv6/udp_impl.h b/net/ipv6/udp_impl.h
index 8a406be25a3a..1bd4a573e1bb 100644
--- a/net/ipv6/udp_impl.h
+++ b/net/ipv6/udp_impl.h
@@ -22,8 +22,7 @@ int udpv6_getsockopt(struct sock *sk, int level, int optname,
 int udpv6_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
 		     unsigned int optlen);
 int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len);
-int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags,
-		  int *addr_len);
+int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags);
 void udpv6_destroy_sock(struct sock *sk);
 
 #ifdef CONFIG_PROC_FS