netdev - [PATCH net v2 1/2] socket: fix option SO_TIMESTAMPING

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Date:   Mon, 12 Oct 2020 11:35:41 +0200
From:   Christian Eggers <ceggers@...i.de>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Willem de Bruijn <willemb@...gle.com>
CC:     Christoph Hellwig <hch@....de>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Christian Eggers <ceggers@...i.de>,
        "Willem de Bruijn" <willemdebruijn.kernel@...il.com>
Subject: [PATCH net v2 1/2] socket: fix option SO_TIMESTAMPING_NEW

The comparison of optname with SO_TIMESTAMPING_NEW is wrong way around,
so SOCK_TSTAMP_NEW will first be set and than reset again. Additionally
move it out of the test for SOF_TIMESTAMPING_RX_SOFTWARE as this seems
unrelated.

This problem happens on 32 bit platforms were the libc has already
switched to struct timespec64 (from SO_TIMExxx_OLD to SO_TIMExxx_NEW
socket options). ptp4l complains with "missing timestamp on transmitted
peer delay request" because the wrong format is received (and
discarded).

Fixes: 9718475e6908 ("socket: Add SO_TIMESTAMPING_NEW")
Signed-off-by: Christian Eggers <ceggers@...i.de>
Reviewed-by: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Reviewed-by: Deepa Dinamani <deepa.kernel@...il.com>
---
v2:
-----
- integrated proposal from Willem de Bruijn
- added Reviewed-by: from Willem and Deepa


On Saturday, 10 October 2020, 02:23:10 CEST, Willem de Bruijn wrote:
> This suggested fix still sets and clears the flag if calling
> SO_TIMESTAMPING_NEW to disable timestamping. 
where is it cleared?

> Instead, how about
> 
>         case SO_TIMESTAMPING_NEW:
> -               sock_set_flag(sk, SOCK_TSTAMP_NEW);
>                 fallthrough;
>         case SO_TIMESTAMPING_OLD:
> [..]
> +               sock_valbool_flag(sk, SOCK_TSTAMP_NEW,
> +                                 optname == SO_TIMESTAMPING_NEW);
> +
using you version looks clearer

>                 if (val & SOF_TIMESTAMPING_OPT_ID &&
> 
I would like to keep this below the "ret = -FOO; break" statements. IMHO the
setsockopt() call should either completely fail or succeed.

 net/core/sock.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 34a8d12e38d7..669cf9b8bb44 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -994,8 +994,6 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		__sock_set_timestamps(sk, valbool, true, true);
 		break;
 	case SO_TIMESTAMPING_NEW:
-		sock_set_flag(sk, SOCK_TSTAMP_NEW);
-		fallthrough;
 	case SO_TIMESTAMPING_OLD:
 		if (val & ~SOF_TIMESTAMPING_MASK) {
 			ret = -EINVAL;
@@ -1024,16 +1022,14 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		}
 
 		sk->sk_tsflags = val;
+		sock_valbool_flag(sk, SOCK_TSTAMP_NEW, optname == SO_TIMESTAMPING_NEW);
+
 		if (val & SOF_TIMESTAMPING_RX_SOFTWARE)
 			sock_enable_timestamp(sk,
 					      SOCK_TIMESTAMPING_RX_SOFTWARE);
-		else {
-			if (optname == SO_TIMESTAMPING_NEW)
-				sock_reset_flag(sk, SOCK_TSTAMP_NEW);
-
+		else
 			sock_disable_timestamp(sk,
 					       (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE));
-		}
 		break;
 
 	case SO_RCVLOWAT:
-- 
Christian Eggers
Embedded software developer

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