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Commit 49ca0d8b authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

net-timestamp: no-payload option 



Add timestamping option SOF_TIMESTAMPING_OPT_TSONLY. For transmit
timestamps, this loops timestamps on top of empty packets.

Doing so reduces the pressure on SO_RCVBUF. Payload inspection and
cmsg reception (aside from timestamps) are no longer possible. This
works together with a follow on patch that allows administrators to
only allow tx timestamping if it does not loop payload or metadata.

Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>

----

Changes (rfc -> v1)
  - add documentation
  - remove unnecessary skb->len test (thanks to Richard Cochran)
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9766e97a

Documentation/networking/timestamping.txt

+21 −0
Original line number Diff line number Diff line
@@ -162,6 +162,27 @@ SOF_TIMESTAMPING_OPT_CMSG: 
  option IP_PKTINFO simultaneously.





SOF_TIMESTAMPING_OPT_TSONLY:



  Applies to transmit timestamps only. Makes the kernel return the

  timestamp as a cmsg alongside an empty packet, as opposed to

  alongside the original packet. This reduces the amount of memory

  charged to the socket's receive budget (SO_RCVBUF) and delivers

  the timestamp even if sysctl net.core.tstamp_allow_data is 0.

  This option disables SOF_TIMESTAMPING_OPT_CMSG.





New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to

disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate

regardless of the setting of sysctl net.core.tstamp_allow_data.



An exception is when a process needs additional cmsg data, for

instance SOL_IP/IP_PKTINFO to detect the egress network interface.

Then pass option SOF_TIMESTAMPING_OPT_CMSG. This option depends on

having access to the contents of the original packet, so cannot be

combined with SOF_TIMESTAMPING_OPT_TSONLY.





1.4 Bytestream Timestamps



The SO_TIMESTAMPING interface supports timestamping of bytes in a

include/uapi/linux/net_tstamp.h

+2 −1
Original line number Diff line number Diff line
@@ -24,8 +24,9 @@ enum { 
	SOF_TIMESTAMPING_TX_SCHED = (1<<8),

	SOF_TIMESTAMPING_TX_ACK = (1<<9),

	SOF_TIMESTAMPING_OPT_CMSG = (1<<10),

	SOF_TIMESTAMPING_OPT_TSONLY = (1<<11),



	SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_CMSG,

	SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_TSONLY,

	SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |

				 SOF_TIMESTAMPING_LAST

};

net/core/skbuff.c

+14 −5
Original line number Diff line number Diff line
@@ -3710,19 +3710,28 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb, 
		     struct sock *sk, int tstype)

{

	struct sk_buff *skb;

	bool tsonly = sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TSONLY;



	if (!sk)

		return;



	if (hwtstamps)

		*skb_hwtstamps(orig_skb) = *hwtstamps;

	if (tsonly)

		skb = alloc_skb(0, GFP_ATOMIC);

	else

		orig_skb->tstamp = ktime_get_real();



		skb = skb_clone(orig_skb, GFP_ATOMIC);

	if (!skb)

		return;



	if (tsonly) {

		skb_shinfo(skb)->tx_flags = skb_shinfo(orig_skb)->tx_flags;

		skb_shinfo(skb)->tskey = skb_shinfo(orig_skb)->tskey;

	}



	if (hwtstamps)

		*skb_hwtstamps(skb) = *hwtstamps;

	else

		skb->tstamp = ktime_get_real();



	__skb_complete_tx_timestamp(skb, sk, tstype);

}

EXPORT_SYMBOL_GPL(__skb_tstamp_tx);

net/ipv4/ip_sockglue.c

+4 −3
Original line number Diff line number Diff line
@@ -483,7 +483,7 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len) 


	serr = SKB_EXT_ERR(skb);



	if (sin) {

	if (sin && skb->len) {

		sin->sin_family = AF_INET;

		sin->sin_addr.s_addr = *(__be32 *)(skb_network_header(skb) +

						   serr->addr_offset);
@@ -496,8 +496,9 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len) 
	sin = &errhdr.offender;

	memset(sin, 0, sizeof(*sin));



	if (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP ||

	    ipv4_pktinfo_prepare_errqueue(sk, skb, serr->ee.ee_origin)) {

	if (skb->len &&

	    (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP ||

	     ipv4_pktinfo_prepare_errqueue(sk, skb, serr->ee.ee_origin))) {

		sin->sin_family = AF_INET;

		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;

		if (inet_sk(sk)->cmsg_flags)

net/ipv6/datagram.c

+2 −3
Original line number Diff line number Diff line
@@ -369,7 +369,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len) 


	serr = SKB_EXT_ERR(skb);



	if (sin) {

	if (sin && skb->len) {

		const unsigned char *nh = skb_network_header(skb);

		sin->sin6_family = AF_INET6;

		sin->sin6_flowinfo = 0;
@@ -394,8 +394,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len) 
	memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));

	sin = &errhdr.offender;

	memset(sin, 0, sizeof(*sin));



	if (serr->ee.ee_origin != SO_EE_ORIGIN_LOCAL) {

	if (serr->ee.ee_origin != SO_EE_ORIGIN_LOCAL && skb->len) {

		sin->sin6_family = AF_INET6;

		if (np->rxopt.all) {

			if (serr->ee.ee_origin != SO_EE_ORIGIN_ICMP &&