Since 5cd1adba79 ("Update to current iptables headers") compilation
of iproute2 broke for systems without iptables-devel package [1].
Reason is that even though we fall back to build m_ipt.c, the include
depends on a xtables-version.h header, which only ships with
iptables-devel. Machines not having this package fail compilation with:
[...]
CC m_ipt.o
In file included from ../include/iptables.h:5:0,
from m_ipt.c:17:
../include/xtables.h:34:29: fatal error: xtables-version.h: No such file or directory
compilation terminated.
../Config:31: recipe for target 'm_ipt.o' failed
make[1]: *** [m_ipt.o] Error 1
The configure script only barks that package xtables was not found in
the pkg-config search path. The generated Config then only contains f.e.
TC_CONFIG_IPSET. In tc's Makefile we thus fall back to adding m_ipt.o
to TCMODULES. m_ipt.c then includes the local include/iptables.h header
copy, which includes the include/xtables.h copy. Latter then includes
xtables-version.h, which only ships with iptables-devel.
One way to resolve this is to skip this whole mess when pkg-config has
no xtables config available. I've carried something along these lines
locally for a while now, but it's just too annyoing. :/ Build works fine
now also when xtables.pc is not available.
[1] http://www.spinics.net/lists/netdev/msg366162.html
Fixes: 5cd1adba79 ("Update to current iptables headers")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Kernel code and interface.
--------------------------
* Compile time switches
There is only one, but very important, compile time switch.
It is not settable by "make config", but should be selected
manually and after a bit of thinking in <include/net/pkt_sched.h>
PSCHED_CLOCK_SOURCE can take three values:
PSCHED_GETTIMEOFDAY
PSCHED_JIFFIES
PSCHED_CPU
PSCHED_GETTIMEOFDAY
Default setting is the most conservative PSCHED_GETTIMEOFDAY.
It is very slow both because of weird slowness of do_gettimeofday()
and because it forces code to use unnatural "timeval" format,
where microseconds and seconds fields are separate.
Besides that, it will misbehave, when delays exceed 2 seconds
(f.e. very slow links or classes bounded to small slice of bandwidth)
To resume: as only you will get it working, select correct clock
source and forget about PSCHED_GETTIMEOFDAY forever.
PSCHED_JIFFIES
Clock is derived from jiffies. On architectures with HZ=100
granularity of this clock is not enough to make reasonable
bindings to real time. However, taking into account Linux
architecture problems, which force us to use artificial
integrated clock in any case, this switch is not so bad
for schduling even on high speed networks, though policing
is not reliable.
PSCHED_CPU
It is available only for alpha and pentiums with correct
CPU timestamp. It is the fastest way, use it when it is available,
but remember: not all pentiums have this facility, and
a lot of them have clock, broken by APM etc. etc.
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