#!/bin/sh -euf
#
# SPDX-License-Identifier: AGPL-3.0-or-later
#
# PASST - Plug A Simple Socket Transport
# for qemu/UNIX domain socket mode
#
# PASTA - Pack A Subtle Tap Abstraction
# for network namespace/tap device mode
#
# slirp4netns.sh - Compatibility wrapper for pasta, behaving like slirp4netns(1)
#
# WARNING: Draft quality, not really tested, --enable-sandbox not supported yet
#
# Copyright (c) 2021 Red Hat GmbH
# Author: Stefano Brivio <sbrivio@redhat.com>
PASTA_PID="$(mktemp)"
PASTA_OPTS="-q --ipv4-only -a 10.0.2.0 -n 24 -g 10.0.2.2 -m 1500 --no-ndp --no-dhcpv6 --no-dhcp -P ${PASTA_PID}"
# add() - Add single option to $PASTA_OPTS
# $1: Option name, with or without argument
add() {
PASTA_OPTS="${PASTA_OPTS} ${1}"
}
# drop() - Drop one option (without argument) from $PASTA_OPTS
# $1: Option name
drop() {
old_opts="${PASTA_OPTS}"; PASTA_OPTS=
for o in ${old_opts}; do [ "${o}" != "${1}" ] && add "${o}"; done
}
# sub() - Substitute option in $PASTA_OPTS, with or without argument
# $1: Option name
# $2: Option argument, can be empty
sub() {
old_opts="${PASTA_OPTS}"; PASTA_OPTS=
next=0
for o in ${old_opts}; do
if [ ${next} -eq 1 ]; then
next=0; add "${1} ${2}"; shift; shift; continue
fi
for r in ${@}; do [ "${o}" = "${r}" ] && next=1 && break; done
[ "${next}" -eq 0 ] && add "${o}"
done
}
# xorshift() - pseudorandom permutation of 16-bit group
# $1: 16-bit value to shuffle
xorshift() {
# Adaptation of Xorshift algorithm from:
# Marsaglia, G. (2003). Xorshift RNGs.
# Journal of Statistical Software, 8(14), 1 - 6.
# doi:http://dx.doi.org/10.18637/jss.v008.i14
# with triplet (5, 3, 1), suitable for 16-bit ranges.
n=${1}
: $((n ^= n << 5))
: $((n ^= n >> 3))
: $((n ^= n << 1))
echo ${n}
}
# opt() - Validate single option from getopts
# $1: Option type
# $@: Variable names to assign to
opt() {
case "${1}" in
u32)
if ! printf "%i" "${OPTARG}" >/dev/null 2>&1 || \
[ "${OPTARG}" -lt 0 ]; then
echo "${OPT} must be a non-negative integer"
usage
fi
eval ${2}="${OPTARG}"
;;
mtu)
if ! printf "%i" "${OPTARG}" >/dev/null 2>&1 || \
[ "${OPTARG}" -lt 0 ] || [ "${OPTARG}" -ge 65522 ]; then
echo "MTU must be a positive integer (< 65522)"
usage
fi
eval ${2}="${OPTARG}"
;;
str)
eval ${2}="${OPTARG}"
;;
net4)
addr="${OPTARG%/*}"
mask="${OPTARG##*/}"
{ [ -z "${mask}" ] || !printf "%i" "${mask}" >/dev/null 2>&1 \
|| [ ${mask} -gt 32 ] || ${mask} -le 0 ]; } && usage
expr "${addr}" : \
'[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$' \
>/dev/null
[ $? -ne 0 ] && usage
ifs="${IFS}"; IFS='.'
for q in ${addr}; do [ ${q} -gt 255 ] && usage; done
IFS="${ifs}"
eval ${2}="${addr}"
eval ${3}="${mask}"
;;
esac
}
# usage() - Print slirpnetns(1) usage and exit indicating failure
# $1: Invalid option name, if any
usage() {
[ ${#} -eq 1 ] && printf "s: invalid option -- '%s'\n" "${0}" "${1}"
cat << EOF
Usage: ${0} [OPTION]... PID|PATH TAPNAME
User-mode networking for unprivileged network namespaces.
-c, --configure bring up the interface
-e, --exit-fd=FD specify the FD for terminating slirp4netns
-r, --ready-fd=FD specify the FD to write to when the network is configured
-m, --mtu=MTU specify MTU (default=1500, max=65521)
-6, --enable-ipv6 enable IPv6 (experimental)
-a, --api-socket=PATH specify API socket path
--cidr=CIDR specify network address CIDR (default=10.0.2.0/24)
--disable-host-loopback prohibit connecting to 127.0.0.1:* on the host namespace
--netns-type=TYPE specify network namespace type ([path|pid], default=pid)
--userns-path=PATH specify user namespace path
--enable-sandbox create a new mount namespace (and drop all caps except CAP_NET_BIND_SERVICE if running as the root)
--enable-seccomp enable seccomp to limit syscalls (experimental)
-h, --help show this help and exit
-v, --version show version and exit
EOF
exit 1
}
# version() - Print version
version() {
echo "slirp4netns-like wrapper for pasta"
exit 0
}
# gen_addr6() - Generate pseudorandom IPv6 address, changes every second
gen_addr6() {
printf "fd00"
n=$(($(xorshift $(date +%S)) % 65536))
for i in $(seq 2 8); do
printf ":%04x" ${n}
n=$(($(xorshift ${n}) % 65536))
done
}
# Default options
v6=0
get_pid=0
MTU=1500
A4="10.0.2.0"
M4="255.255.255.0"
no_map_gw=0
EFD=0
RFD=0
while getopts ce:r:m:6a:hv-: OPT 2>/dev/null; do
if [ "${OPT}" = "-" ]; then
OPT="${OPTARG%%[= ]*}"
OPTARG="${OPTARG#${OPT}[= ]}"
fi
case "${OPT}" in
c | configure) add "--config-net" ;;
e | exit-fd) opt u32 EFD ;;
r | ready-fd) opt u32 RFD ;;
m | mtu) opt mtu MTU && sub -m ${MTU} ;;
6 | enable-ipv6) V6=1 ;;
a | api-socket) opt str API ;;
cidr) opt net4 A4 M4 && sub -a ${A4} -n ${M4} ;;
disable-host-loopback) add "--no-map-gw" && no_map_gw=1 ;;
netns-type) : Autodetected ;;
userns-path) opt_str USERNS_NAME "${OPTARG}" ;;
enable-sandbox) : Not supported yet ;;
enable-seccomp) : Cannot be disabled ;;
h | help) usage "${0}" ;;
v | version) version ;;
??*) usage "${0}" "${OPT}" ;;
?) usage "${0}" ;;
esac
done
shift $((OPTIND - 1))
[ ${#} -ne 2 ] && usage
ns_spec="${1}"
ifname="${2}"
add "-I ${ifname}"
if [ ${v6} -eq 1 ]; then
drop "--ipv4-only"
add "-a $(gen_addr6) -g fd00::2 -D fd00::3"
fi
./pasta ${PASTA_OPTS} ${ns_spec} 2>/dev/null && \
[ ${RFD} -ne 0 ] && echo "1" >&${RFD}
trap "kill $(cat ${PASTA_PID}); rm ${PASTA_PID}" INT TERM
cat << EOF
sent tapfd=5 for ${ifname}
received tapfd=5
Starting slirp
* MTU: ${MTU}
* Network: ${A4}
* Netmask: ${M4}
* Gateway: 10.0.2.2
* DNS: 10.0.2.3
* Recommended IP: 10.0.2.100
EOF
if [ ${no_map_gw} -eq 0 ]; then
echo "WARNING: 127.0.0.1:* on the host is accessible as 10.0.2.2 (set --disable-host-loopback to prohibit connecting to 127.0.0.1:*)"
fi
if [ ${EFD} -ne 0 ]; then
dd count=1 of=/dev/null 2>/dev/null <&${EFD}
else
while read a; do :; done
fi
exit 0
