#!/bin/bash # dhclient-script for Linux. Dan Halbert, March, 1997. # Updated for Linux 2.[12] by Brian J. Murrell, January 1999. # No guarantees about this. I'm a novice at the details of Linux # networking. # Notes: # 0. This script is based on the netbsd script supplied with dhcp-970306. # 1. ifconfig down apparently deletes all relevant routes and flushes # the arp cache, so this doesn't need to be done explicitly. # 2. The alias address handling here has not been tested AT ALL. # I'm just going by the doc of modern Linux ip aliasing, which uses # notations like eth0:0, eth0:1, for each alias. # 3. I have to calculate the network address, and calculate the broadcast # address if it is not supplied. This might be much more easily done # by the dhclient C code, and passed on. # 4. TIMEOUT not tested. ping has a flag I don't know, and I'm suspicious # of the $1 in its args. # 5. Script refresh in 2017. The aliasing code was too convoluted and needs # to go away. Migrated DHCPv4 script to ip command from iproute2 suite. # This is based on Debian script with some tweaks. ifconfig is no longer # used. Everything is done using ip tool from ip-route2. # 'ip' just looks too weird. Also, we now have unit-tests! Those unit-tests # overwirte this line to use a fake ip-echo tool. It's also convenient # if your system holds ip tool in a non-standard location. ip=/sbin/ip # update /etc/resolv.conf based on received values # This updated version mostly follows Debian script by Andrew Pollock et al. make_resolv_conf() { local new_resolv_conf # DHCPv4 if [ -n "$new_domain_search" ] || [ -n "$new_domain_name" ] || [ -n "$new_domain_name_servers" ]; then new_resolv_conf=/etc/resolv.conf.dhclient-new rm -f $new_resolv_conf if [ -n "$new_domain_name" ]; then echo domain ${new_domain_name%% *} >>$new_resolv_conf fi if [ -n "$new_domain_search" ]; then if [ -n "$new_domain_name" ]; then domain_in_search_list="" for domain in $new_domain_search; do if [ "$domain" = "${new_domain_name}" ] || [ "$domain" = "${new_domain_name}." ]; then domain_in_search_list="Yes" fi done if [ -z "$domain_in_search_list" ]; then new_domain_search="$new_domain_name $new_domain_search" fi fi echo "search ${new_domain_search}" >> $new_resolv_conf elif [ -n "$new_domain_name" ]; then echo "search ${new_domain_name}" >> $new_resolv_conf fi if [ -n "$new_domain_name_servers" ]; then for nameserver in $new_domain_name_servers; do echo nameserver $nameserver >>$new_resolv_conf done else # keep 'old' nameservers sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p /etc/resolv.conf >>$new_resolv_conf fi if [ -f /etc/resolv.conf ]; then chown --reference=/etc/resolv.conf $new_resolv_conf chmod --reference=/etc/resolv.conf $new_resolv_conf fi mv -f $new_resolv_conf /etc/resolv.conf # DHCPv6 elif [ -n "$new_dhcp6_domain_search" ] || [ -n "$new_dhcp6_name_servers" ]; then new_resolv_conf=/etc/resolv.conf.dhclient-new rm -f $new_resolv_conf if [ -n "$new_dhcp6_domain_search" ]; then echo "search ${new_dhcp6_domain_search}" >> $new_resolv_conf fi if [ -n "$new_dhcp6_name_servers" ]; then for nameserver in $new_dhcp6_name_servers; do # append %interface to link-local-address nameservers if [ "${nameserver##fe80::}" != "$nameserver" ] || [ "${nameserver##FE80::}" != "$nameserver" ]; then nameserver="${nameserver}%${interface}" fi echo nameserver $nameserver >>$new_resolv_conf done else # keep 'old' nameservers sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p /etc/resolv.conf >>$new_resolv_conf fi if [ -f /etc/resolv.conf ]; then chown --reference=/etc/resolv.conf $new_resolv_conf chmod --reference=/etc/resolv.conf $new_resolv_conf fi mv -f $new_resolv_conf /etc/resolv.conf fi } # set host name set_hostname() { local current_hostname if [ -n "$new_host_name" ]; then current_hostname=$(hostname) # current host name is empty, '(none)' or 'localhost' or differs from new one from DHCP if [ -z "$current_hostname" ] || [ "$current_hostname" = '(none)' ] || [ "$current_hostname" = 'localhost' ] || [ "$current_hostname" = "$old_host_name" ]; then if [ "$new_host_name" != "$old_host_name" ]; then hostname "$new_host_name" fi fi fi } # run given script run_hook() { local script local exit_status script="$1" if [ -f $script ]; then . $script fi if [ -n "$exit_status" ] && [ "$exit_status" -ne 0 ]; then logger -p daemon.err "$script returned non-zero exit status $exit_status" fi return $exit_status } # run scripts in given directory run_hookdir() { local dir local exit_status dir="$1" if [ -d "$dir" ]; then for script in $(run-parts --list $dir); do run_hook $script || true exit_status=$? done fi return $exit_status } # Must be used on exit. Invokes the local dhcp client exit hooks, if any. exit_with_hooks() { exit_status=$1 # Source the documented exit-hook script, if it exists if ! run_hook /etc/dhclient-exit-hooks; then exit_status=$? fi # Now run scripts in the Debian-specific directory. if ! run_hookdir /etc/dhclient-exit-hooks.d; then exit_status=$? fi exit $exit_status } # This function was largely borrowed from dhclient-script that # ships with Centos, authored by Jiri Popelka and David Cantrell # of Redhat. Thanks guys. add_ipv6_addr_with_DAD() { ${ip} -6 addr replace ${new_ip6_address}/${new_ip6_prefixlen} \ dev ${interface} scope global valid_lft ${new_max_life} \ preferred_lft ${new_preferred_life} if [ ${dad_wait_time} -le 0 ] then # if we're not waiting for DAD, assume we're good return 0 fi # Repeatedly test whether newly added address passed # duplicate address detection (DAD) for i in $(seq 1 ${dad_wait_time}); do sleep 1 # give the DAD some time addr=$(${ip} -6 addr show dev ${interface} \ | grep ${new_ip6_address}/${new_ip6_prefixlen}) # tentative flag == DAD is still not complete tentative=$(echo "${addr}" | grep tentative) # dadfailed flag == address is already in use somewhere else dadfailed=$(echo "${addr}" | grep dadfailed) if [ -n "${dadfailed}" ] ; then # address was added with valid_lft/preferred_lft 'forever', # remove it ${ip} -6 addr del ${new_ip6_address}/${new_ip6_prefixlen} \ dev ${interface} exit_with_hooks 3 fi if [ -z "${tentative}" ] ; then if [ -n "${addr}" ]; then # DAD is over return 0 else # address was auto-removed (or not added at all) exit_with_hooks 3 fi fi done return 0 } # Invoke the local dhcp client enter hooks, if they exist. run_hook /etc/dhclient-enter-hooks run_hookdir /etc/dhclient-enter-hooks.d # Execute the operation case "$reason" in ### DHCPv4 Handlers MEDIUM|ARPCHECK|ARPSEND) # Do nothing ;; PREINIT) # The DHCP client is requesting that an interface be # configured as required in order to send packets prior to # receiving an actual address. - dhclient-script(8) # ensure interface is up ${ip} link set dev ${interface} up if [ -n "$alias_ip_address" ]; then # flush alias IP from interface ${ip} -4 addr flush dev ${interface} label ${interface}:0 fi ;; BOUND|RENEW|REBIND|REBOOT) set_hostname if [ -n "$old_ip_address" ] && [ -n "$alias_ip_address" ] && [ "$alias_ip_address" != "$old_ip_address" ]; then # alias IP may have changed => flush it ${ip} -4 addr flush dev ${interface} label ${interface}:0 fi if [ -n "$old_ip_address" ] && [ "$old_ip_address" != "$new_ip_address" ]; then # leased IP has changed => flush it ${ip} -4 addr flush dev ${interface} label ${interface} fi if [ -z "$old_ip_address" ] || [ "$old_ip_address" != "$new_ip_address" ] || [ "$reason" = "BOUND" ] || [ "$reason" = "REBOOT" ]; then # new IP has been leased or leased IP changed => set it ${ip} -4 addr add ${new_ip_address}${new_subnet_mask:+/$new_subnet_mask} \ ${new_broadcast_address:+broadcast $new_broadcast_address} \ dev ${interface} label ${interface} if [ -n "$new_interface_mtu" ]; then # set MTU ${ip} link set dev ${interface} mtu ${new_interface_mtu} fi # if we have $new_rfc3442_classless_static_routes then we have to # ignore $new_routers entirely if [ ! "$new_rfc3442_classless_static_routes" ]; then # set if_metric if IF_METRIC is set or there's more than one router if_metric="$IF_METRIC" if [ "${new_routers%% *}" != "${new_routers}" ]; then if_metric=${if_metric:-1} fi for router in $new_routers; do if [ "$new_subnet_mask" = "255.255.255.255" ]; then # point-to-point connection => set explicit route ${ip} -4 route add ${router} dev $interface >/dev/null 2>&1 fi # set default route ${ip} -4 route add default via ${router} dev ${interface} \ ${if_metric:+metric $if_metric} >/dev/null 2>&1 if [ -n "$if_metric" ]; then if_metric=$((if_metric+1)) fi done fi fi if [ -n "$alias_ip_address" ] && [ "$new_ip_address" != "$alias_ip_address" ]; then # separate alias IP given, which may have changed # => flush it, set it & add host route to it ${ip} -4 addr flush dev ${interface} label ${interface}:0 ${ip} -4 addr add ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \ dev ${interface} label ${interface}:0 ${ip} -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1 fi # update /etc/resolv.conf make_resolv_conf ;; EXPIRE|FAIL|RELEASE|STOP) if [ -n "$alias_ip_address" ]; then # flush alias IP ${ip} -4 addr flush dev ${interface} label ${interface}:0 fi if [ -n "$old_ip_address" ]; then # flush leased IP ${ip} -4 addr flush dev ${interface} label ${interface} fi if [ -n "$alias_ip_address" ]; then # alias IP given => set it & add host route to it ${ip} -4 addr add ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \ dev ${interface} label ${interface}:0 ${ip} -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1 fi ;; TIMEOUT) if [ -n "$alias_ip_address" ]; then # flush alias IP ${ip} -4 addr flush dev ${interface} label ${interface}:0 fi # set IP from recorded lease ${ip} -4 addr add ${new_ip_address}${new_subnet_mask:+/$new_subnet_mask} \ ${new_broadcast_address:+broadcast $new_broadcast_address} \ dev ${interface} label ${interface} if [ -n "$new_interface_mtu" ]; then # set MTU ${ip} link set dev ${interface} mtu ${new_interface_mtu} fi # if there is no router recorded in the lease or the 1st router answers pings if [ -z "$new_routers" ] || ping -q -c 1 "${new_routers%% *}"; then # if we have $new_rfc3442_classless_static_routes then we have to # ignore $new_routers entirely if [ ! "$new_rfc3442_classless_static_routes" ]; then if [ -n "$alias_ip_address" ] && [ "$new_ip_address" != "$alias_ip_address" ]; then # separate alias IP given => set up the alias IP & add host route to it ${ip} -4 addr add \ ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \ dev ${interface} label ${interface}:0 ${ip} -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1 fi # set if_metric if IF_METRIC is set or there's more than one router if_metric="$IF_METRIC" if [ "${new_routers%% *}" != "${new_routers}" ]; then if_metric=${if_metric:-1} fi # set default route for router in $new_routers; do ${ip} -4 route add default via ${router} dev ${interface} \ ${if_metric:+metric $if_metric} >/dev/null 2>&1 if [ -n "$if_metric" ]; then if_metric=$((if_metric+1)) fi done fi # update /etc/resolv.conf make_resolv_conf else # flush all IPs from interface ip -4 addr flush dev ${interface} exit_with_hooks 2 fi ;; V6ONLY) if [ -n "$old_ip_address" ]; then # flush leased IP ${ip} -4 addr flush dev ${interface} label ${interface} fi ;; ### DHCPv6 Handlers # TODO handle prefix change: ?based on ${old_ip6_prefix} and ${new_ip6_prefix}? PREINIT6) # ensure interface is up ${ip} link set ${interface} up # We need to give the kernel some time to active interface interface_up_wait_time=5 for i in $(seq 0 ${interface_up_wait_time}) do ${ip} link show dev ${interface} | grep -q LOWER_UP 2>&1 if [ $? -eq 0 ]; then break; fi sleep 1 done # flush any stale global permanent IPs from interface ${ip} -6 addr flush dev ${interface} scope global permanent # Wait for duplicate address detection for this interface if the # --dad-wait-time parameter has been specified and is greater than # zero. if [ ${dad_wait_time} -gt 0 ]; then # Check if any IPv6 address on this interface is marked as # tentative. ${ip} addr show ${interface} | grep inet6 | grep tentative \ &> /dev/null if [ $? -eq 0 ]; then # Wait for duplicate address detection to complete or for # the timeout specified as --dad-wait-time. for i in $(seq 0 $dad_wait_time) do # We're going to poll for the tentative flag every second. sleep 1 ${ip} addr show ${interface} | grep inet6 | grep tentative \ &> /dev/null if [ $? -ne 0 ]; then break; fi done fi fi ;; BOUND6|RENEW6|REBIND6) if [ "${new_ip6_address}" ] && [ "${new_ip6_prefixlen}" ]; then # set leased IP add_ipv6_addr_with_DAD fi # update /etc/resolv.conf if [ "${reason}" = BOUND6 ] || [ "${new_dhcp6_name_servers}" != "${old_dhcp6_name_servers}" ] || [ "${new_dhcp6_domain_search}" != "${old_dhcp6_domain_search}" ]; then make_resolv_conf fi ;; DEPREF6) if [ -z "${cur_ip6_prefixlen}" ]; then exit_with_hooks 2 fi # set preferred lifetime of leased IP to 0 ${ip} -6 addr change ${cur_ip6_address}/${cur_ip6_prefixlen} \ dev ${interface} scope global preferred_lft 0 ;; EXPIRE6|RELEASE6|STOP6) if [ -z "${old_ip6_address}" ] || [ -z "${old_ip6_prefixlen}" ]; then exit_with_hooks 2 fi # delete leased IP ${ip} -6 addr del ${old_ip6_address}/${old_ip6_prefixlen} \ dev ${interface} ;; esac exit_with_hooks 0