The NF_HOOK_COND returns 0 when it shouldn't due to what I believe to be an
error in the code as the order of operations is not what was intended. C will
evalutate == before =. Which means ret is getting set to the bool result,
rather than the return value of the function call. The code says
if (ret = function() == 1)
when it meant to say:
if ((ret = function()) == 1)
Normally the compiler would warn, but it doesn't notice it because its
a actually complex conditional and so the wrong code is wrapped in an explict
set of () [exactly what the compiler wants you to do if this was intentional].
Fixing this means that errors when netfilter denies a packet get propagated
back up the stack rather than lost.
Signed-off-by: Eric Paris <eparis@redhat.com>
---
include/linux/netfilter.h | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 89341c3..03317c8 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -215,7 +215,7 @@ NF_HOOK_COND(uint8_t pf, unsigned int hook, struct sk_buff *skb,
int ret;
if (!cond ||
- (ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, INT_MIN) == 1))
+ ((ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, INT_MIN)) == 1))
ret = okfn(skb);
return ret;
}
--
