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net: simplify flags for tx timestamping

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This patch removes the abstraction introduced by the union skb_shared_tx in
the shared skb data.

The access of the different union elements at several places led to some
confusion about accessing the shared tx_flags e.g. in skb_orphan_try().

    http://marc.info/?l=linux-netdev&m=128084897415886&w=2

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Oliver Hartkopp
2010-08-17 08:59:14 +00:00
committed by David S. Miller
parent 4d5870ec10
commit 2244d07bfa
17 changed files with 68 additions and 87 deletions
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22
Documentation/networking/timestamping.txt
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@@ -172,15 +172,19 @@ struct skb_shared_hwtstamps {
};
Time stamps for outgoing packets are to be generated as follows:
- In hard_start_xmit(), check if skb_tx(skb)->hardware is set no-zero.
If yes, then the driver is expected to do hardware time stamping.
- In hard_start_xmit(), check if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)
is set no-zero. If yes, then the driver is expected to do hardware time
stamping.
- If this is possible for the skb and requested, then declare
that the driver is doing the time stamping by setting the field
skb_tx(skb)->in_progress non-zero. You might want to keep a pointer
to the associated skb for the next step and not free the skb. A driver
not supporting hardware time stamping doesn't do that. A driver must
never touch sk_buff::tstamp! It is used to store software generated
time stamps by the network subsystem.
that the driver is doing the time stamping by setting the flag
SKBTX_IN_PROGRESS in skb_shinfo(skb)->tx_flags , e.g. with
skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
You might want to keep a pointer to the associated skb for the next step
and not free the skb. A driver not supporting hardware time stamping doesn't
do that. A driver must never touch sk_buff::tstamp! It is used to store
software generated time stamps by the network subsystem.
- As soon as the driver has sent the packet and/or obtained a
hardware time stamp for it, it passes the time stamp back by
calling skb_hwtstamp_tx() with the original skb, the raw
@@ -191,6 +195,6 @@ Time stamps for outgoing packets are to be generated as follows:
this would occur at a later time in the processing pipeline than other
software time stamping and therefore could lead to unexpected deltas
between time stamps.
- If the driver did not call set skb_tx(skb)->in_progress, then
- If the driver did not set the SKBTX_IN_PROGRESS flag (see above), then
dev_hard_start_xmit() checks whether software time stamping
is wanted as fallback and potentially generates the time stamp.