src: stricter netlink attribute length validation

If the kernel sends us different data length for a given attribute,
stop further processing and indicate that an ABI breakage has ocurred.
This is an example of the (hypothetical) message that is shown in that
case:

 nf_tables kernel ABI is broken, contact your vendor.
 table.c:214 reason: Numerical result out of range

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/utils.c b/src/utils.c
index 20a2fa3..1878390 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -225,3 +225,10 @@ void __nft_assert_fail(uint16_t attr, const char *filename, int line)
 		attr, filename, line);
 	exit(EXIT_FAILURE);
 }
+
+void __noreturn __abi_breakage(const char *file, int line, const char *reason)
+{
+       fprintf(stderr, "nf_tables kernel ABI is broken, contact your vendor.\n"
+		       "%s:%d reason: %s\n", file, line, reason);
+       exit(EXIT_FAILURE);
+}