nfqueue-loadbalancer - extend or alter

The nfqueue-loadbalancer release includes a development environment that let you extend or alter the nfqlb.

To build the nfqlb binary;

#sudo apt install -y libmnl-dev libnetfilter-queue-dev
export NFQLB_DIR=/path/to/nfqlb-x.y.z  # the release directory
cd $NFQLB_DIR/src
make help
make -j8

New commands

New commands can be added to nfqlb without altering the nfqlb code. This allows you to maintain a modified nfqlb outside, and independent of, the nfqlb repository.

A new command must add itself using a "constructor";

__attribute__ ((__constructor__)) static void addCommands(void) {
        addCmd("xlb", cmdXlb);
}

The constructor is executed before main() (similar to static constructors in C++).

The modified nfqlb then can be built with;

gcc -o mynfqlb -pthread -I$NFQLB_DIR/include cmdXlb.c $NFQLB_DIR/src/*.c \
  -L$NFQLB_DIR/lib -lnfqlb -lmnl -lnetfilter_queue -lrt

An example is included in src/extension;

cd $NFQLB_DIR/src/extension
make help
make -j8

Static build

On Ubuntu static libraries for netfilter_queue are not included so the source must be downloaded and built locally;

cd $NFQLB_DIR/src
./nfqlb.sh libnfqueue_download
./nfqlb.sh libnfqueue_unpack --dest=/tmp/$USER/nfqlb
./nfqlb.sh libnfqueue_build --dest=/tmp/$USER/nfqlb

Now build a statically linked binary with;

export NFQD=/tmp/$USER/nfqlb/libnetfilter_queue-1.0.3/sys/usr/local
cd $NFQLB_DIR/src/extension
#make clean # (remove any lingering dynamic build)
make -j8 static