Implement recursive mutex that works across processes/threads
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oblique
parent
cafef2e185
commit
4ea5d02193
166
create_ap
166
create_ap
@ -23,7 +23,8 @@ export LC_ALL=C
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# all new files and directories must be readable only by root.
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# in special cases we must use chmod to give any other permissions.
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umask 0077
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SCRIPT_UMASK=0077
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umask $SCRIPT_UMASK
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usage() {
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echo "Usage: "$PROGNAME" [options] <wifi-interface> [<interface-with-internet>] [<access-point-name> [<passphrase>]]"
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@ -82,6 +83,78 @@ usage() {
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echo " "$PROGNAME" --stop wlan0"
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}
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# allocate lock for the caller bash thread
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alloc_lock() {
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# lock file for creating mutex
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local LOCK_FILE=/tmp/create_ap.lock
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local LOCK_FD=LOCK_FD_$BASHPID
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# if lock FD is already allocated just return
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eval "[[ \$$LOCK_FD -ne 0 ]]" && return 0
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# use the lowest unused FD. avoid FD 0 because we use it to
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# indicate that LOCK_FD_$BASHPID is not set.
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for x in $(seq 1 $(ulimit -n)); do
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if [[ ! -a "/proc/$BASHPID/fd/$x" ]]; then
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eval "$LOCK_FD=$x"
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# open/create lock file with write access for all users
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# otherwise normal users will not be able to use it.
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# to avoid race conditions on creation, we need to
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# use umask to set the permissions.
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umask 0555
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eval "eval \"exec \$$LOCK_FD>$LOCK_FILE\"" > /dev/null 2>&1 || return 1
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umask $SCRIPT_UMASK
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# there is a case where lock file was created from a normal
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# user. change the owner to root as soon as we can.
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[[ $(id -u) -eq 0 ]] && chown 0:0 $LOCK_FILE
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return 0
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fi
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done
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return 1
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}
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# recursive mutex lock for all create_ap processes/threads.
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#
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# WARNING: if you lock in a function that their caller need their
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# output (i.e. the caller use | or $()) then you can have dead-lock
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# if the caller took the lock before. this happens because bash creates
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# a new thread for the callie function.
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mutex_lock() {
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local MUTEX_COUNTER=MUTEX_COUNTER_$BASHPID
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local LOCK_FD=LOCK_FD_$BASHPID
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# allocate lock FD if needed
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if eval "[[ \$$LOCK_FD -eq 0 ]]"; then
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alloc_lock || die "Failed to allocate lock"
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fi
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# lock if needed and increase the counter
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eval "[[ \$$MUTEX_COUNTER -eq 0 ]]" && eval "flock \$$LOCK_FD"
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eval "$MUTEX_COUNTER=\$(( \$$MUTEX_COUNTER + 1 ))"
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return 0
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}
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# recursive mutex unlock for all create_ap processes/threads
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mutex_unlock() {
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local MUTEX_COUNTER=MUTEX_COUNTER_$BASHPID
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local LOCK_FD=LOCK_FD_$BASHPID
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# if lock FD was not allocated or we didn't lock before
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# then just return
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eval "[[ \$$LOCK_FD -eq 0 || \$$MUTEX_COUNTER -eq 0 ]]" && return 0
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# unlock if needed and decrease the counter
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eval "$MUTEX_COUNTER=\$(( \$$MUTEX_COUNTER - 1 ))"
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eval "[[ \$$MUTEX_COUNTER -eq 0 ]]" && eval "flock -u \$$LOCK_FD"
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return 0
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}
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# it takes 2 arguments
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# returns:
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# 0 if v1 (1st argument) and v2 (2nd argument) are the same
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@ -246,24 +319,30 @@ get_macaddr() {
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get_avail_bridge() {
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local i=0
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mutex_lock
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while :; do
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if ! is_interface br${i}; then
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mutex_unlock
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echo br${i}
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return
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fi
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i=$((i + 1))
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done
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mutex_unlock
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}
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get_virt_iface_name() {
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local i=0
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mutex_lock
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while :; do
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if ! is_interface ap${i}; then
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mutex_unlock
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echo ap${i}
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return
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fi
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i=$((i+1))
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done
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mutex_unlock
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}
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get_all_macaddrs() {
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@ -274,10 +353,12 @@ get_new_macaddr() {
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local OLDMAC NEWMAC LAST_BYTE i
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OLDMAC=$(get_macaddr "$1")
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LAST_BYTE=$(printf %d 0x${OLDMAC##*:})
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mutex_lock
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for i in {1..255}; do
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NEWMAC="${OLDMAC%:*}:$(printf %02x $(( ($LAST_BYTE + $i) % 256 )))"
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(get_all_macaddrs | grep "$NEWMAC" > /dev/null 2>&1) || break
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done
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mutex_unlock
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echo $NEWMAC
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}
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@ -285,6 +366,7 @@ get_new_macaddr() {
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haveged_watchdog() {
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local show_warn=1
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while :; do
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mutex_lock
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if [[ $(cat /proc/sys/kernel/random/entropy_avail) -lt 1000 ]]; then
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if ! which haveged > /dev/null 2>&1; then
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if [[ $show_warn -eq 1 ]]; then
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@ -297,9 +379,11 @@ haveged_watchdog() {
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haveged -w 1024 -F > /dev/null 2>&1 &
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local haveged_pid=$!
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echo $haveged_pid > $CONFDIR/haveged.pid
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mutex_unlock
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wait $haveged_pid
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fi
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fi
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mutex_unlock
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sleep 2
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done
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}
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@ -354,14 +438,20 @@ networkmanager_add_unmanaged() {
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[[ -z "$MAC" ]] && return 1
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fi
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mutex_lock
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UNMANAGED=$(grep -m1 -Eo '^unmanaged-devices=[[:alnum:]:;,-]*' /etc/NetworkManager/NetworkManager.conf)
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WAS_EMPTY=0
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[[ -z "$UNMANAGED" ]] && WAS_EMPTY=1
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UNMANAGED=$(echo "$UNMANAGED" | sed 's/unmanaged-devices=//' | tr ';,' ' ')
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# if it exists, do nothing
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for x in $UNMANAGED; do
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[[ $x == "mac:${MAC}" ]] && return 2
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[[ $NM_OLDER_VERSION -eq 0 && $x == "interface-name:${1}" ]] && return 2
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if [[ $x == "mac:${MAC}" ]] ||
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[[ $NM_OLDER_VERSION -eq 0 && $x == "interface-name:${1}" ]]; then
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mutex_unlock
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return 2
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fi
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done
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if [[ $NM_OLDER_VERSION -eq 1 ]]; then
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@ -383,6 +473,7 @@ networkmanager_add_unmanaged() {
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fi
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ADDED_UNMANAGED="${ADDED_UNMANAGED} ${1} "
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mutex_unlock
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return 0
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}
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@ -401,9 +492,13 @@ networkmanager_rm_unmanaged() {
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[[ -z "$MAC" ]] && return 1
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fi
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mutex_lock
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UNMANAGED=$(grep -m1 -Eo '^unmanaged-devices=[[:alnum:]:;,-]*' /etc/NetworkManager/NetworkManager.conf | sed 's/unmanaged-devices=//' | tr ';,' ' ')
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[[ -z "$UNMANAGED" ]] && return 1
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if [[ -z "$UNMANAGED" ]]; then
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mutex_unlock
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return 1
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fi
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[[ -n "$MAC" ]] && UNMANAGED=$(echo $UNMANAGED | sed -e "s/mac:${MAC}\( \|$\)//g")
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UNMANAGED=$(echo $UNMANAGED | sed -e "s/interface-name:${1}\( \|$\)//g")
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@ -418,13 +513,16 @@ networkmanager_rm_unmanaged() {
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fi
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ADDED_UNMANAGED="${ADDED_UNMANAGED/ ${1} /}"
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mutex_unlock
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return 0
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}
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networkmanager_fix_unmanaged() {
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[[ -f ${NETWORKMANAGER_CONF} ]] || return
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mutex_lock
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sed -e "/^unmanaged-devices=.*/d" -i ${NETWORKMANAGER_CONF}
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mutex_unlock
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}
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networkmanager_rm_unmanaged_if_needed() {
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@ -482,8 +580,9 @@ HAVEGED_WATCHDOG_PID=
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_cleanup() {
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local PID x
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trap "" SIGINT
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trap "" SIGUSR1
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mutex_lock
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trap "" SIGINT SIGUSR1 SIGUSR2
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# kill haveged_watchdog
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[[ -n "$HAVEGED_WATCHDOG_PID" ]] && kill $HAVEGED_WATCHDOG_PID
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@ -569,6 +668,8 @@ _cleanup() {
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fi
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networkmanager_rm_unmanaged_if_needed ${WIFI_IFACE} ${OLD_MACADDR}
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fi
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mutex_unlock
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}
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cleanup() {
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@ -580,15 +681,33 @@ cleanup() {
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die() {
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[[ -n "$1" ]] && echo -e "\nERROR: $1\n" >&2
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cleanup
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exit 1
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# we cleanup and exit only if we are the main thread
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if [[ $$ -eq $BASHPID ]]; then
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cleanup
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exit 1
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else
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# send die signal to the main thread
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kill -USR2 $$
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# terminate our thread
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kill -9 $BASHPID
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fi
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}
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clean_exit() {
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cleanup
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exit 0
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# we cleanup and exit only if we are the main thread
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if [[ $$ -eq $BASHPID ]]; then
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cleanup
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exit 0
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else
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# send clean_exit signal to the main thread
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kill -USR1 $$
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# terminate our thread
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kill -9 $BASHPID
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fi
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}
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# WARNING: never call mutex_lock in this function, otherwise we
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# will have dead-lock when send_stop is called
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list_running() {
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local PID IFACE x
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for x in /tmp/create_ap.*; do
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@ -610,9 +729,11 @@ is_running_pid() {
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send_stop() {
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local x
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mutex_lock
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# send stop signal to specific pid
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if is_running_pid $1; then
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kill -USR1 $1
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mutex_unlock
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return
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fi
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@ -620,12 +741,9 @@ send_stop() {
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for x in $(list_running | grep -E " ${1}\$" | cut -f1 -d' '); do
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kill -USR1 $x
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done
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mutex_unlock
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}
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# if the user press ctrl+c then execute die()
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trap "clean_exit" SIGINT
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trap "clean_exit" SIGUSR1
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ARGS=( "$@" )
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GETOPT_ARGS=$(getopt -o hc:w:g:dnm: -l "help","hidden","ieee80211n","ht_capab:","driver:","no-virt","fix-unmanaged","country:","freq-band:","mac:","daemon","stop:","list","version","no-haveged" -n "$PROGNAME" -- "$@")
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[[ $? -ne 0 ]] && exit 1
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@ -740,8 +858,22 @@ if [[ $# -lt 1 && $FIX_UNMANAGED -eq 0 && -z "$STOP_ID" && $LIST_RUNNING -eq 0
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exit 1
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fi
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# allocate lock for the main thread to avoid any failures later
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if ! alloc_lock; then
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echo "ERROR: Failed to allocate lock" >&2
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exit 1
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fi
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# if the user press ctrl+c or we get USR1 signal
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# then run clean_exit()
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trap "clean_exit" SIGINT SIGUSR1
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# if we get USR2 signal then run die().
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trap "die" SIGUSR2
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if [[ $LIST_RUNNING -eq 1 ]]; then
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mutex_lock
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list_running
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mutex_unlock
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exit 0
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fi
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@ -951,6 +1083,7 @@ if [[ $NO_VIRT -eq 1 && "$WIFI_IFACE" == "$INTERNET_IFACE" ]]; then
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exit 1
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fi
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mutex_lock
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CONFDIR=$(mktemp -d /tmp/create_ap.${WIFI_IFACE}.conf.XXXXXXXX)
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echo "Config dir: $CONFDIR"
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echo "PID: $$"
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@ -960,6 +1093,7 @@ echo $$ > $CONFDIR/pid
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# permitions to $CONFDIR and $CONFDIR/pid
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chmod 755 $CONFDIR
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chmod 444 $CONFDIR/pid
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mutex_unlock
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if [[ $NO_VIRT -eq 0 ]]; then
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VWIFI_IFACE=$(get_virt_iface_name)
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@ -1198,10 +1332,6 @@ fi
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# start access point
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echo "hostapd command-line interface: hostapd_cli -p $CONFDIR/hostapd_ctrl"
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# from now on we exit with 0 on SIGINT
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trap "clean_exit" SIGINT
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trap "clean_exit" SIGUSR1
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if [[ $NO_HAVEGED -eq 0 ]]; then
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haveged_watchdog &
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HAVEGED_WATCHDOG_PID=$!
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