Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Signed-off-by: Nicolas Thill <nico@openwrt.org>

- Avoid non-pointer use of `FILE` type since its just a forward declaration
 - Build with -D_GNU_SOURCE to expose required `struct tcphdr` members

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

Fixes https://github.com/openwrt/packages/issues/908

Signed-off-by: Daniel Golle <daniel@makrotopia.org>