sock: enable timestamping using control messages

Currently, SOL_TIMESTAMPING can only be enabled using setsockopt.
This is very costly when users want to sample writes to gather
tx timestamps.

Add support for enabling SO_TIMESTAMPING via control messages by
using tsflags added in `struct sockcm_cookie` (added in the previous
patches in this series) to set the tx_flags of the last skb created in
a sendmsg. With this patch, the timestamp recording bits in tx_flags
of the skbuff is overridden if SO_TIMESTAMPING is passed in a cmsg.

Please note that this is only effective for overriding the recording
timestamps flags. Users should enable timestamp reporting (e.g.,
SOF_TIMESTAMPING_SOFTWARE | SOF_TIMESTAMPING_OPT_ID) using
socket options and then should ask for SOF_TIMESTAMPING_TX_*
using control messages per sendmsg to sample timestamps for each
write.

Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 5 deletions

diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 088ce665fc7b..438f50c1a676 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -339,8 +339,8 @@ int raw_rcv(struct sock *sk, struct sk_buff *skb)
 
 static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4,
                            struct msghdr *msg, size_t length,
-                           struct rtable **rtp,
-                           unsigned int flags)
+                           struct rtable **rtp, unsigned int flags,
+                           const struct sockcm_cookie *sockc)
 {
         struct inet_sock *inet = inet_sk(sk);
         struct net *net = sock_net(sk);
@@ -379,7 +379,7 @@ static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4,
 
         skb->ip_summed = CHECKSUM_NONE;
 
-        sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
+        sock_tx_timestamp(sk, sockc->tsflags, &skb_shinfo(skb)->tx_flags);
 
         skb->transport_header = skb->network_header;
         err = -EFAULT;
@@ -540,6 +540,7 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
                 daddr = inet->inet_daddr;
         }
 
+        ipc.sockc.tsflags = sk->sk_tsflags;
         ipc.addr = inet->inet_saddr;
         ipc.opt = NULL;
         ipc.tx_flags = 0;
@@ -638,10 +639,10 @@ back_from_confirm:
 
         if (inet->hdrincl)
                 err = raw_send_hdrinc(sk, &fl4, msg, len,
-                                      &rt, msg->msg_flags);
+                                      &rt, msg->msg_flags, &ipc.sockc);
 
          else {
-                sock_tx_timestamp(sk, &ipc.tx_flags);
+                sock_tx_timestamp(sk, ipc.sockc.tsflags, &ipc.tx_flags);
 
                 if (!ipc.addr)
                         ipc.addr = fl4.daddr;