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>

2 files changed, 10 insertions, 6 deletions

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index d0aeb97aec5d..55ee1eb7d026 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -867,7 +867,8 @@ int ip6_append_data(struct sock *sk,
                                 int odd, struct sk_buff *skb),
                     void *from, int length, int transhdrlen, int hlimit,
                     int tclass, struct ipv6_txoptions *opt, struct flowi6 *fl6,
-                    struct rt6_info *rt, unsigned int flags, int dontfrag);
+                    struct rt6_info *rt, unsigned int flags, int dontfrag,
+                    const struct sockcm_cookie *sockc);
 
 int ip6_push_pending_frames(struct sock *sk);
 
@@ -884,7 +885,8 @@ struct sk_buff *ip6_make_skb(struct sock *sk,
                              void *from, int length, int transhdrlen,
                              int hlimit, int tclass, struct ipv6_txoptions *opt,
                              struct flowi6 *fl6, struct rt6_info *rt,
-                             unsigned int flags, int dontfrag);
+                             unsigned int flags, int dontfrag,
+                             const struct sockcm_cookie *sockc);
 
 static inline struct sk_buff *ip6_finish_skb(struct sock *sk)
 {
diff --git a/include/net/sock.h b/include/net/sock.h
index af012da5e608..e91b87f54f99 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2057,19 +2057,21 @@ static inline void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
                 sk->sk_stamp = skb->tstamp;
 }
 
-void __sock_tx_timestamp(const struct sock *sk, __u8 *tx_flags);
+void __sock_tx_timestamp(__u16 tsflags, __u8 *tx_flags);
 
 /**
  * sock_tx_timestamp - checks whether the outgoing packet is to be time stamped
  * @sk:         socket sending this packet
+ * @tsflags:    timestamping flags to use
  * @tx_flags:   completed with instructions for time stamping
  *
  * Note : callers should take care of initial *tx_flags value (usually 0)
  */
-static inline void sock_tx_timestamp(const struct sock *sk, __u8 *tx_flags)
+static inline void sock_tx_timestamp(const struct sock *sk, __u16 tsflags,
+                                     __u8 *tx_flags)
 {
-        if (unlikely(sk->sk_tsflags))
-                __sock_tx_timestamp(sk, tx_flags);
+        if (unlikely(tsflags))
+                __sock_tx_timestamp(tsflags, tx_flags);
         if (unlikely(sock_flag(sk, SOCK_WIFI_STATUS)))
                 *tx_flags |= SKBTX_WIFI_STATUS;
 }