#!/bin/sh

# This must run as root as CTDB tool commands need to access CTDB socket
[ "$(id -u)" -eq 0 ] || exec sudo "$0" "$@"

# statd must be configured to use this script as its high availability call-out.
#
# In most Linux versions this can be done using something like the following...
#
# /etc/sysconfig/nfs (Red Hat) or /etc/default/nfs-common (Debian):
#   NFS_HOSTNAME=myhostname
#   STATD_HOSTNAME="${NFS_HOSTNAME} -H /etc/ctdb/statd-callout"
#
# Newer Red Hat Linux variants instead use /etc/nfs.conf:
#   [statd]
#     name = myhostname
#     ha-callout = /etc/ctdb/statd-callout

[ -n "$CTDB_BASE" ] || \
    CTDB_BASE=$(d=$(dirname "$0") ; cd -P "$d" ; echo "$PWD")

. "${CTDB_BASE}/functions"

# Overwrite this so we get some logging
die ()
{
    script_log "statd-callout" "$@"
    exit 1
}

# Try different variables to find config file for NFS_HOSTNAME
load_system_config "nfs" "nfs-common"

# If NFS_HOSTNAME not set then try to pull it out of /etc/nfs.conf
if [ -z "$NFS_HOSTNAME" ] && type nfsconf >/dev/null 2>&1 ; then
	NFS_HOSTNAME=$(nfsconf --get statd name)
fi

[ -n "$NFS_HOSTNAME" ] || \
    die "NFS_HOSTNAME is not configured. statd-callout failed"

############################################################

ctdb_setup_state_dir "service" "nfs"

# script_state_dir set by ctdb_setup_state_dir()
# shellcheck disable=SC2154
d="${script_state_dir}/statd-callout"

mkdir -p "$d" || die "Failed to create directory \"${d}\""
cd "$d" || die "Failed to change directory to \"${d}\""

pnn=$(ctdb_get_pnn)

############################################################

send_notifies ()
{
	_smnotify="${CTDB_HELPER_BINDIR}/smnotify"

	# State must monotonically increase, across the entire
	# cluster.  Use seconds since epoch and hope the time is in
	# sync across nodes.  Even numbers mean service is shut down,
	# odd numbers mean service is started.

	# Intentionally round to an even number
	# shellcheck disable=SC2017
	_state_even=$(( $(date '+%s') / 2 * 2))

	_prev=""
	while read _sip _cip ; do
		# NOTE: Consider optimising smnotify to read all the
		# data from stdin and then run it in the background.

		# Reset stateval for each serverip
		if [ "$_sip" != "$_prev" ] ; then
			_stateval="$_state_even"
		fi

		# Send notifies for server shutdown
		"$_smnotify" --client="$_cip" --ip="$_sip" \
			     --server="$_sip" --stateval="$_stateval"
		"$_smnotify" --client="$_cip" --ip="$_sip" \
			     --server="$NFS_HOSTNAME" --stateval="$_stateval"

		# Send notifies for server startup
		_stateval=$((_stateval + 1))
		"$_smnotify" --client="$_cip" --ip="$_sip" \
			     --server="$_sip" --stateval="$_stateval"
		"$_smnotify" --client="$_cip" --ip="$_sip" \
			     --server="$NFS_HOSTNAME" --stateval="$_stateval"
	done
}

delete_records ()
{
	while read _sip _cip ; do
		_key="statd-state@${_sip}@${_cip}"
		echo "\"${_key}\" \"\""
	done | $CTDB ptrans "ctdb.tdb"
}

############################################################

case "$1" in
    # Keep a single file to keep track of the last "add-client" or
    # "del-client'.  These get pushed to ctdb.tdb during "update",
    # which will generally be run once each "monitor" cycle.  In this
    # way we avoid scalability problems with flood of persistent
    # transactions after a "notify" when all the clients re-take their
    # locks.

    add-client)
	# statd does not tell us to which IP the client connected so
	# we must add it to all the IPs that we serve
	cip="$2"
	date=$(date '+%s')
	# x is intentionally ignored
	# shellcheck disable=SC2034
	$CTDB ip -X |
	tail -n +2 |
	while IFS="|" read x sip node x ; do
	    [ "$node" = "$pnn" ] || continue # not us
	    key="statd-state@${sip}@${cip}"
	    echo "\"${key}\" \"${date}\"" >"$key"
	done
	;;

    del-client)
	# statd does not tell us from which IP the client disconnected
	# so we must add it to all the IPs that we serve
	cip="$2"
	# x is intentionally ignored
	# shellcheck disable=SC2034
	$CTDB ip -X |
	tail -n +2 |
	while IFS="|" read x sip node x ; do
	    [ "$node" = "$pnn" ] || continue # not us
	    key="statd-state@${sip}@${cip}"
	    echo "\"${key}\" \"\"" >"$key"
	done
	;;

    update)
        files=$(echo statd-state@*)
	if [ "$files" = "statd-state@*" ] ; then
	    # No files!
	    exit 0
	fi
	# Filter out lines for any IP addresses that are not currently
	# hosted public IP addresses.
	ctdb_ips=$($CTDB ip | tail -n +2)
	sed_expr=$(echo "$ctdb_ips" |
	    awk -v pnn="$pnn" 'pnn == $2 {
                ip = $1; gsub(/\./, "\\.", ip);
                printf "/statd-state@%s@/p\n", ip }')
	# Intentional multi-word expansion for multiple files
	# shellcheck disable=SC2086
	items=$(sed -n "$sed_expr" $files)
	if [ -n "$items" ] ; then
		if echo "$items"  | $CTDB ptrans "ctdb.tdb" ; then
			# shellcheck disable=SC2086
			rm $files
		fi
	fi
	;;

    notify)
	# we must restart the lockmanager (on all nodes) so that we get
	# a clusterwide grace period (so other clients don't take out
	# conflicting locks through other nodes before all locks have been
	# reclaimed)

	# we need these settings to make sure that no tcp connections survive
	# across a very fast failover/failback
	#echo 10 > /proc/sys/net/ipv4/tcp_fin_timeout
	#echo 0 > /proc/sys/net/ipv4/tcp_max_tw_buckets
	#echo 0 > /proc/sys/net/ipv4/tcp_max_orphans

	# Delete the notification list for statd, we don't want it to 
	# ping any clients
	rm -f /var/lib/nfs/statd/sm/*
	rm -f /var/lib/nfs/statd/sm.bak/*

	# We must also let some time pass between stopping and
	# restarting the lock manager.  Otherwise there is a window
	# where the lock manager will respond "strangely" immediately
	# after restarting it, which causes clients to fail to reclaim
	# their locks.
	nfs_callout_init
	"$CTDB_NFS_CALLOUT" "stop" "nlockmgr" >/dev/null 2>&1
        sleep 2
	"$CTDB_NFS_CALLOUT" "start" "nlockmgr" >/dev/null 2>&1

	# we now need to send out additional statd notifications to ensure
	# that clients understand that the lockmanager has restarted.
	# we have three cases:
	# 1, clients that ignore the ip address the stat notification came from
	#    and ONLY care about the 'name' in the notify packet.
	#    these clients ONLY work with lock failover IFF that name
	#    can be resolved into an ipaddress that matches the one used
	#    to mount the share.  (==linux clients)
	#    This is handled when starting lockmanager above,  but those
	#    packets are sent from the "wrong" ip address, something linux
	#    clients are ok with, buth other clients will barf at.
	# 2, Some clients only accept statd packets IFF they come from the
	#    'correct' ip address.
	# 2a,Send out the notification using the 'correct' ip address and also
	#    specify the 'correct' hostname in the statd packet.
	#    Some clients require both the correct source address and also the
	#    correct name. (these clients also ONLY work if the ip addresses
	#    used to map the share can be resolved into the name returned in
	#    the notify packet.)
	# 2b,Other clients require that the source ip address of the notify
	#    packet matches the ip address used to take out the lock.
	#    I.e. that the correct source address is used.
	#    These clients also require that the statd notify packet contains
	#    the name as the ip address used when the lock was taken out.
	#
	# Both 2a and 2b are commonly used in lockmanagers since they maximize
	# probability that the client will accept the statd notify packet and
	# not just ignore it.
	# For all IPs we serve, collect info and push to the config database

	# Construct a sed expression to take catdb output and produce pairs of:
	#   server-IP client-IP
	# but only for the server-IPs that are hosted on this node.
	ctdb_all_ips=$($CTDB ip all | tail -n +2)
	sed_expr=$(echo "$ctdb_all_ips" |
	    awk -v pnn="$pnn" 'pnn == $2 {
                ip = $1; gsub(/\./, "\\.", ip);
                printf "s/^key.*=.*statd-state@\\(%s\\)@\\([^\"]*\\).*/\\1 \\2/p\n", ip }')

	statd_state=$($CTDB catdb ctdb.tdb | sed -n "$sed_expr" | sort)
	[ -n "$statd_state" ] || exit 0

	echo "$statd_state" | send_notifies
	echo "$statd_state" | delete_records

	# Remove any stale touch files (i.e. for IPs not currently
	# hosted on this node and created since the last "update").
	# There's nothing else we can do with them at this stage.
	echo "$ctdb_all_ips" |
	    awk -v pnn="$pnn" 'pnn != $2 { print $1 }' |
	    while read sip ; do
		rm -f "statd-state@${sip}@"*
	    done
	;;
esac