cd /usr/src
wget ftp://ftp3.usa.openbsd.org/pub/OpenBSD/4.2/sys.tar.gz
wget ftp://ftp.openbsd.org/pub/OpenBSD/patches/4.2/common/004_pf.patch
wget ftp://ftp.openbsd.org/pub/OpenBSD/patches/4.2/common/005_ifrtlabel.patch
wget ftp://ftp.openbsd.org/pub/OpenBSD/patches/4.2/common/007_tcprespond.patch
wget ftp://ftp.openbsd.org/pub/OpenBSD/patches/4.2/common/008_ip6rthdr.patch
tar zxvf sys.tar.gz
patch -p0 < 004_pf.patch
patch -p0 < 005_ifrtlabel.patch
patch -p0 < 007_tcprespond.patch
patch -p0 < 008_ip6rthdr.patch
cd /usr/src/sys/arch/`arch -s`/conf
config GENERIC && cd ../compile/GENERIC
make depend && make && sudo make install
reboot