[PATCH net-next v2 v2 2/2] net: mctp: support MSG_ERRQUEUE in recvmsg()

[Jian Zhang]

This enables userspace to retrieve struct sock_extended_err for
locally detected transmit failures, using the standard socket
error queue mechanism.

At this point, only the generic errno information is reported.
No MCTP-specific control messages or extended error details are
provided.

Signed-off-by: Jian Zhang <zhangjian.3032@xxxxxxxxxxxxx>
---
 net/mctp/af_mctp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index 209a963112e3..353599812a0a 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -291,9 +291,12 @@ static int mctp_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 	u8 type;
 	int rc;
 
-	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC | MSG_PEEK))
+	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC | MSG_PEEK | MSG_ERRQUEUE))
 		return -EOPNOTSUPP;
 
+	if (flags & MSG_ERRQUEUE)
+		return sock_recv_errqueue(sk, msg, len, SOL_MCTP, 0);
+
 	skb = skb_recv_datagram(sk, flags, &rc);
 	if (!skb)
 		return rc;
-- 
2.20.1