When a helper module is unloaded all conntracks refering to it have their
helper pointer NULLed out, leading to lots of races. In most places this
can be fixed by proper use of RCU (they do already check for != NULL,
but in a racy way), additionally nf_conntrack_expect_related needs to
bail out when no helper is present.

Also remove two paranoid BUG_ONs in nf_conntrack_proto_gre that are racy
and not worth fixing.
Signed-off-by: NPatrick McHarrdy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

- move EXPORT_SYMBOL next to exported symbol
- use EXPORT_SYMBOL_GPL since this is what the original code used
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Some helpers (namely H.323) manually assign further helpers to expected
connections. This is not possible with nf_conntrack anymore since we
need to know whether a helper is used at allocation time.

Handle the helper assignment centrally, which allows to perform the
correct allocation and as a nice side effect eliminates the need
for the H.323 helper to fiddle with nf_conntrack_lock.

Mid term the allocation scheme really needs to be redesigned since
we do both the helper and expectation lookup _twice_ for every new
connection.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Adding the alignment to the size doesn't make any sense, what it
should do is align the size of the conntrack structure to the
alignment requirements of the helper structure and return an
aligned pointer in nfct_help().
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NPatrick McHardy <kaber@trash.net>

Rename 'struct nf_conntrack_protocol' to 'struct nf_conntrack_l4proto' in
order to help distinguish it from 'struct nf_conntrack_l3proto'. It gets
rather confusing with 'nf_conntrack_protocol'.
Signed-off-by: NMartin Josefsson <gandalf@wlug.westbo.se>
Signed-off-by: NPatrick McHardy <kaber@trash.net>

Place rarely written variables in the read-mostly section by using
__read_mostly
Signed-off-by: NMartin Josefsson <gandalf@wlug.westbo.se>
Signed-off-by: NPatrick McHardy <kaber@trash.net>

This patch splits out handling of helpers into its own file
nf_conntrack_helper.c
Signed-off-by: NMartin Josefsson <gandalf@wlug.westbo.se>
Signed-off-by: NPatrick McHardy <kaber@trash.net>