RE: [PATCH/RFC] packet: fix sock_tx_timestamp() in packet_snd() via sendto syscall

Hi,

From: Willem de Bruijn
Sent: Saturday, July 16, 2016 12:31 AM

On Thu, Jul 14, 2016 at 10:49 PM, Yoshihiro Shimoda
[off-list ref] wrote:

quoted

Since the sendto syscall doesn't have msg_control buffer,
the sock_tx_timestamp() in packet_snd() cannot work correctly because
the socks.fsflags is set to 0.

You're right. __sock_tx_timestamp used to take sk->sk_tsflags as
input, now it relies solely on this parameter tsflags. All callsites
must either pass sk->sk_tsflags directly or initialize sockc.tsflags
to this value.

Thank you very much for the comment!

quoted

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9f0983f..d76fd41 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c

@@ -2887,6 +2887,11 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
                err = sock_cmsg_send(sk, msg, &sockc);
                if (unlikely(err))
                        goto out_unlock;
+       } else {
+               /* Set tsflags from sk because a syscall (e.g. sendto) doesn't
+                * have msg_control buffer.
+                */
+               sockc.tsflags = sk->sk_tsflags;
        }

Better to follow the example of other protocols. In all three packet
variants, make the following initialization change:

-       sockc.tsflags = 0;
+       sockc.tsflags = sk->sk_tsflags;

Thank you for the suggestion. I submitted a fixed patch now.

Best regards,
Yoshihiro Shimoda

(I had to remove some recipients, because my reply was marked as spam
and dropped otherwise..)