ip: remove tx_flags from ipcm_cookie and use same logic for v4 and v6

skb_shinfo(skb)->tx_flags is derived from sk->sk_tsflags, possibly
after modification by __sock_cmsg_send, by calling sock_tx_timestamp.

The IPv4 and IPv6 paths do this conversion differently. In IPv4, the
individual protocols that support tx timestamps call this function
and store the result in ipc.tx_flags. In IPv6, sock_tx_timestamp is
called in __ip6_append_data.

There is no need to store both tx_flags and ts_flags in the cookie
as one is derived from the other. Convert when setting up the cork
and remove the redundant field. This is similar to IPv6, only have
the conversion happen only once per datagram, in ip(6)_setup_cork.

Also change __ip6_append_data to match __ip_append_data. Only update
tskey if timestamping is enabled with OPT_ID. The SOCK_.. test is
redundant: only valid protocols can have non-zero cork->tx_flags.

After this change the IPv4 and IPv6 logic is the same.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip.h

@@ -72,7 +72,6 @@ struct ipcm_cookie {
 	__be32			addr;
 	int			oif;
 	struct ip_options_rcu	*opt;
-	__u8			tx_flags;
 	__u8			ttl;
 	__s16			tos;
 	char			priority;

net/ipv4/ip_output.c

@@ -1153,8 +1153,9 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
 	cork->ttl = ipc->ttl;
 	cork->tos = ipc->tos;
 	cork->priority = ipc->priority;
-	cork->tx_flags = ipc->tx_flags;
 	cork->transmit_time = ipc->sockc.transmit_time;
+	cork->tx_flags = 0;
+	sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
 
 	return 0;
 }

net/ipv4/ping.c

@@ -763,8 +763,6 @@ static int ping_v4_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		rcu_read_unlock();
 	}
 
-	sock_tx_timestamp(sk, ipc.sockc.tsflags, &ipc.tx_flags);
-
 	saddr = ipc.addr;
 	ipc.addr = faddr = daddr;
 

net/ipv4/raw.c

@@ -665,8 +665,6 @@ static int raw_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 				      &rt, msg->msg_flags, &ipc.sockc);
 
 	 else {
-		sock_tx_timestamp(sk, ipc.sockc.tsflags, &ipc.tx_flags);
-
 		if (!ipc.addr)
 			ipc.addr = fl4.daddr;
 		lock_sock(sk);

net/ipv4/udp.c

@@ -1020,8 +1020,6 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	saddr = ipc.addr;
 	ipc.addr = faddr = daddr;
 
-	sock_tx_timestamp(sk, ipc.sockc.tsflags, &ipc.tx_flags);
-
 	if (ipc.opt && ipc.opt->opt.srr) {
 		if (!daddr) {
 			err = -EINVAL;

net/ipv6/ip6_output.c

@@ -1221,6 +1221,8 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
 	cork->base.fragsize = mtu;
 	cork->base.gso_size = sk->sk_type == SOCK_DGRAM &&
 			      sk->sk_protocol == IPPROTO_UDP ? ipc6->gso_size : 0;
+	cork->base.tx_flags = 0;
+	sock_tx_timestamp(sk, ipc6->sockc.tsflags, &cork->base.tx_flags);
 
 	if (dst_allfrag(xfrm_dst_path(&rt->dst)))
 		cork->base.flags |= IPCORK_ALLFRAG;
@@ -1250,7 +1252,6 @@ static int __ip6_append_data(struct sock *sk,
 	int copy;
 	int err;
 	int offset = 0;
-	__u8 tx_flags = 0;
 	u32 tskey = 0;
 	struct rt6_info *rt = (struct rt6_info *)cork->dst;
 	struct ipv6_txoptions *opt = v6_cork->opt;
@@ -1269,6 +1270,10 @@ static int __ip6_append_data(struct sock *sk,
 	mtu = cork->gso_size ? IP6_MAX_MTU : cork->fragsize;
 	orig_mtu = mtu;
 
+	if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
+	    sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
+		tskey = sk->sk_tskey++;
+
 	hh_len = LL_RESERVED_SPACE(rt->dst.dev);
 
 	fragheaderlen = sizeof(struct ipv6hdr) + rt->rt6i_nfheader_len +
@@ -1318,13 +1323,6 @@ static int __ip6_append_data(struct sock *sk,
 	    rt->dst.dev->features & (NETIF_F_IPV6_CSUM | NETIF_F_HW_CSUM))
 		csummode = CHECKSUM_PARTIAL;
 
-	if (sk->sk_type == SOCK_DGRAM || sk->sk_type == SOCK_RAW) {
-		sock_tx_timestamp(sk, ipc6->sockc.tsflags, &tx_flags);
-		if (tx_flags & SKBTX_ANY_SW_TSTAMP &&
-		    sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
-			tskey = sk->sk_tskey++;
-	}
-
 	/*
 	 * Let's try using as much space as possible.
 	 * Use MTU if total length of the message fits into the MTU.
@@ -1443,8 +1441,8 @@ static int __ip6_append_data(struct sock *sk,
 				    dst_exthdrlen);
 
 			/* Only the initial fragment is time stamped */
-			skb_shinfo(skb)->tx_flags = tx_flags;
-			tx_flags = 0;
+			skb_shinfo(skb)->tx_flags = cork->tx_flags;
+			cork->tx_flags = 0;
 			skb_shinfo(skb)->tskey = tskey;
 			tskey = 0;