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net-timestamp: no-payload option

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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: Willem de Bruijn <willemb@google.com>

----

Changes (rfc -> v1)
  - add documentation
  - remove unnecessary skb->len test (thanks to Richard Cochran)
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2015-01-30 13:29:31 -05:00 committed by David S. Miller
parent 9766e97af1
commit 49ca0d8bfa
6 changed files with 48 additions and 12 deletions
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21
Documentation/networking/timestamping.txt
View File

@ -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

3
include/uapi/linux/net_tstamp.h
View File

@ -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
};

19
net/core/skbuff.c
View File

@ -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);
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);

7
net/ipv4/ip_sockglue.c
View File

@ -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)

5
net/ipv6/datagram.c
View File

@ -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 &&

5
net/rxrpc/ar-error.c
View File

@ -42,6 +42,11 @@ void rxrpc_UDP_error_report(struct sock *sk)
_leave("UDP socket errqueue empty");
return;
}
if (!skb->len) {
_leave("UDP empty message");
kfree_skb(skb);
return;
}
rxrpc_new_skb(skb);