Download libpcap-X.Y.tar.gz from http://www.tcpdump.org/#latest-release
and verify the signature.

cd
# Make a copy of this directory.
cp -r ~/nmap/libpcap/NMAP_MODIFICATIONS .
tar xzvf libpcap-X.Y.tar.gz
cd nmap
rsync -rv --delete ~/libpcap-X.Y/ ~/nmap/libpcap/
git add -A libpcap
cd libpcap
# Apply the pre-configure patch.
git apply -p0 --directory=libpcap/ ~/NMAP_MODIFICATIONS/pre-configure.patch
./configure
make grammar.c scanner.c scanner.h tokdefs.h
git add grammar.c scanner.c scanner.h tokdefs.h
cd ..
# Apply patches.
git apply -p0 --directory=libpcap/ ~/NMAP_MODIFICATIONS/000*
cd libpcap
autoconf
cd ..
git add -u libpcap
mv ~/NMAP_MODIFICATIONS libpcap/
git add libpcap/NMAP_MODIFICATIONS
git commit -m "Upgrade libpcap to X.Y."