can: raw: add support for SO_TXTIME/SCM_TXTIME

This patch calls into sock_cmsg_send() to parse the user supplied
control information into a struct sockcm_cookie. Then assign the
requested transmit time to the skb.

This makes it possible to use the Earliest TXTIME First (ETF) packet
scheduler with the CAN_RAW protocol. The user can send a CAN_RAW frame
with a TXTIME and the kernel (with the ETF scheduler) will take care
of sending it to the network interface.

Link: https://lore.kernel.org/all/20220502091946.1916211-3-mkl@pengutronix.de
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/net/can/raw.c b/net/can/raw.c
index 1a68efa..d1bd9cc 100644 (file)
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -772,6 +772,7 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 {
        struct sock *sk = sock->sk;
        struct raw_sock *ro = raw_sk(sk);
+       struct sockcm_cookie sockc;
        struct sk_buff *skb;
        struct net_device *dev;
        int ifindex;
@@ -817,10 +818,18 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
        if (err < 0)
                goto free_skb;
 
-       skb_setup_tx_timestamp(skb, sk->sk_tsflags);
+       sockcm_init(&sockc, sk);
+       if (msg->msg_controllen) {
+               err = sock_cmsg_send(sk, msg, &sockc);
+               if (unlikely(err))
+                       goto free_skb;
+       }
 
        skb->dev = dev;
        skb->priority = sk->sk_priority;
+       skb->tstamp = sockc.transmit_time;
+
+       skb_setup_tx_timestamp(skb, sockc.tsflags);
 
        err = can_send(skb, ro->loopback);