iputils: add README.md

iputils/README.md

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+# iputils
+
+Build the [iputils](https://github.com/iputils/iputils/) set of tools as static PIE ELF binaries running on Linux.
+
+## Requirements
+
+Make sure the following packages are installed:
+* gcc >= 8 (required for the `-static-pie` linking option)
+* autotools
+* meson
+* GNU Make
+
+For Debian, run the command below to install all requirements:
+
+```bash
+$ sudo apt install build-essential
+export DEBIAN_FRONTEND="noninteractive"
+
+apt update
+
+apt install -y --no-install-recommends \
+	clang \
+	docbook-xsl-ns \
+	file \
+	gcc \
+	gettext \
+	iproute2 \
+	libcap-dev \
+	libidn2-0-dev \
+	libssl-dev \
+	make \
+	meson \
+	pkg-config \
+	xsltproc
+
+```
+
+## Building
+
+The static PIE ELF file are located in the current directory.
+If you want to rebuild them, run:
+
+```bash
+$ ./build.sh
+```
+
+This script downloads, unpacks, patches, configures and builds the tools.
+
+## Running
+
+The resulting binaries can be used as is.
+For example, you can ping an address by issuing the command:
+
+```bash
+$ ./ping 1.1.1.1
+```
+
+## Issues
+
+1. When running in KVM with LWIP you can't use RAW sockets because they're not
+   available by default. See this for more information:
+   https://github.com/unikraft/lib-lwip/pull/2
+
+2. There is a bug in LWIP where normal sockets (not RAW) that use ICMP protocol
+   are sent using UDP protocol instead. See https://github.com/unikraft/lib-lwip/issues/32