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Date:   Tue, 1 Mar 2022 15:44:53 +0100
From:   Samuel Thibault <samuel.thibault@labri.fr>
To:     willemb@google.com
Cc:     davem@davemloft.net, kuba@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] SO_ZEROCOPY should rather return -ENOPROTOOPT
Message-ID: <20220301144453.snstwdjy3kmpi4zf@begin>
Mail-Followup-To: Samuel Thibault <samuel.thibault@labri.fr>,
        willemb@google.com, davem@davemloft.net, kuba@kernel.org,
        linux-kernel@vger.kernel.org
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ENOTSUPP is documented as "should never be seen by user programs", and
is not exposed in <errno.h>, so applications cannot safely check against
it. We should rather return the well-known -ENOPROTOOPT.

Signed-off-by: Samuel Thibault <samuel.thibault@labri.fr>

diff --git a/net/core/sock.c b/net/core/sock.c
index 4ff806d71921..6e5b84194d56 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1377,9 +1377,9 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 			if (!(sk_is_tcp(sk) ||
 			      (sk->sk_type == SOCK_DGRAM &&
 			       sk->sk_protocol == IPPROTO_UDP)))
-				ret = -ENOTSUPP;
+				ret = -ENOPROTOOPT;
 		} else if (sk->sk_family != PF_RDS) {
-			ret = -ENOTSUPP;
+			ret = -ENOPROTOOPT;
 		}
 		if (!ret) {
 			if (val < 0 || val > 1)