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Date: Sun, 20 Apr 2008 22:35:21 -0700
From: Jason Uhlenkott <juhlenko@...mai.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org,
Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: [RFC 2/4] net core: let protocols implement SOCK_TIMESTAMP efficiently
Classically, if anyone enabled the SOCK_TIMESTAMP flag on any socket
(via the SO_TIMESTAMP socket option or the SIOCGSTAMP ioctl), we'd
start recording timestamps for *every* packet coming into the system.
We did this because timestamps were recorded very early by the net
core, before the upper protocol layers had a chance to look up the
socket(s) associated with each incoming packet.
This gives protocols a way to announce (via a new flag,
PROTO_HAS_SOCK_TIMESTAMP) that they'll record packet timestamps
themselves, *after* the socket lookup has happened, so timestamps on
supported socket types can be enabled on a per-socket basis, instead
of globally in the net core.
For most protocols, supporting this is trivial: it just requires a
call to sock_timestamp(sk, skb) somewhere in the rcv path, typically
immediately after the socket lookup.
Signed-off-by: Jason Uhlenkott <juhlenko@...mai.com>
---
include/net/sock.h | 13 +++++++++++++
net/core/sock.c | 21 +++++++++++++++++++--
2 files changed, 32 insertions(+), 2 deletions(-)
Index: linux/include/net/sock.h
===================================================================
--- linux.orig/include/net/sock.h 2008-04-20 21:03:54.000000000 -0700
+++ linux/include/net/sock.h 2008-04-20 21:04:03.000000000 -0700
@@ -475,6 +475,12 @@
skb->next = NULL;
}
+static inline void sock_timestamp(struct sock *sk, struct sk_buff *skb)
+{
+ if (sock_flag(sk, SOCK_TIMESTAMP) && !skb->tstamp.tv64)
+ __net_timestamp(skb);
+}
+
#define sk_wait_event(__sk, __timeo, __condition) \
({ int __rc; \
release_sock(__sk); \
@@ -587,6 +593,8 @@
char name[32];
struct list_head node;
+
+ unsigned long flags;
#ifdef SOCK_REFCNT_DEBUG
atomic_t socks;
#endif
@@ -595,6 +603,11 @@
extern int proto_register(struct proto *prot, int alloc_slab);
extern void proto_unregister(struct proto *prot);
+enum proto_flags {
+ /* proto handles per-socket timestamp flag efficiently */
+ PROTO_HAS_SOCK_TIMESTAMP = 0,
+};
+
#ifdef SOCK_REFCNT_DEBUG
static inline void sk_refcnt_debug_inc(struct sock *sk)
{
Index: linux/net/core/sock.c
===================================================================
--- linux.orig/net/core/sock.c 2008-04-20 21:03:54.000000000 -0700
+++ linux/net/core/sock.c 2008-04-20 21:04:03.000000000 -0700
@@ -287,11 +287,27 @@
}
EXPORT_SYMBOL(sock_get_timestampns);
+/*
+ * Does this type of socket implement SOCK_TIMESTAMP efficiently (by
+ * calling sock_timestamp() in the upper protocol layers, after we've
+ * looked up the skb's socket)?
+ */
+static inline int sock_supports_timestamps(struct sock *sk)
+{
+ return sk->sk_prot->flags & (1 << PROTO_HAS_SOCK_TIMESTAMP);
+}
+
void sock_enable_timestamp(struct sock *sk)
{
if (!sock_flag(sk, SOCK_TIMESTAMP)) {
sock_set_flag(sk, SOCK_TIMESTAMP);
- net_enable_timestamp();
+ if (!sock_supports_timestamps(sk)) {
+ /*
+ * Ugh, we can't enable timestamps for just
+ * this socket. We'll have to do it globally.
+ */
+ net_enable_timestamp();
+ }
}
}
@@ -299,7 +315,8 @@
{
if (sock_flag(sk, SOCK_TIMESTAMP)) {
sock_reset_flag(sk, SOCK_TIMESTAMP);
- net_disable_timestamp();
+ if (!sock_supports_timestamps(sk))
+ net_disable_timestamp();
}
}
--
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