Routers with multiple "dirty" interfaces
My apologies for asking something here which is not strictly an ARM
question, but I thought I'd run it past the local experts before raising
my head in somewhere like LKML.
I'm tinkering with some systems (mostly RPis with pukka "Jessie") for
routing work, which have multiple "dirty" bearer interfaces with a
tunnel to an ISP on top expected to use the route with the
numerically-lowest metric.
Potentially, the bearers come up and go down in an arbitrary sequence,
with each event triggering a small number of iptables commands. When the
first interface- whichever it is- comes up various table policies and
global rules will be established, and when the last interface goes down
the tables will be flushed to their default state. That raises two
questions:
a) Am I correct in believing that Debian's handling of
/etc/network/interfaces is single-threaded (non-reentrant)?
b) Is it safe to use /proc/sys/net/ipv4/ip_forward (and the various
rp_filter and log_martians states) as counters?
So far (b) appears to work, but I'm interested to know whether this is
by design or by luck.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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