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ctdb-doc: Improve 10.interface documentation and comments

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Signed-off-by: Martin Schwenke <mschwenke@ddn.com>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jerry Heyman <jheyman@ddn.com>
This commit is contained in:
Martin Schwenke 2023-08-22 12:12:50 +10:00 committed by Martin Schwenke
parent 60067e2a74
commit 025bd34dfc
2 changed files with 26 additions and 21 deletions
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42
ctdb/config/events/legacy/10.interface.script
View File

@ -1,9 +1,7 @@
#!/bin/sh
#################################
# interface event script for ctdb
# this adds/removes IPs from your
# public interface
# Handle public IP address release and takeover, as well as monitoring
# interfaces used by public IP addresses.
[ -n "$CTDB_BASE" ] || \
CTDB_BASE=$(d=$(dirname "$0") && cd -P "$d" && dirname "$PWD")
@ -125,8 +123,8 @@ init)
get_proc "$_promote" >/dev/null 2>&1 || \
die "Public IPs only supported if promote_secondaries is available"
# make sure we drop any ips that might still be held if
# previous instance of ctdb got killed with -9 or similar
# Make sure we drop any IPs that might still be held if
# previous instance of ctdbd got killed with -9 or similar
drop_all_public_ips
;;
@ -156,12 +154,15 @@ takeip)
;;
releaseip)
# releasing an IP is a bit more complex than it seems. Once the IP
# is released, any open tcp connections to that IP on this host will end
# up being stuck. Some of them (such as NFS connections) will be unkillable
# so we need to use the killtcp ctdb function to kill them off. We also
# need to make sure that no new connections get established while we are
# doing this! So what we do is this:
# Releasing an IP is a bit more complex than it seems. Once
# the IP is released, any open TCP connections to that IP on
# this host will end up being stuck. Some of them (such as NFS
# connections) will be unkillable so we need to terminate
# them. We also need to make sure that no new connections get
# established while we are doing this.
#
# The steps are:
#
# 1) firewall this IP, so no new external packets arrive for it
# 2) find existing connections, and kill them
# 3) remove the IP from the interface
@ -186,17 +187,20 @@ releaseip)
;;
updateip)
# moving an IP is a bit more complex than it seems.
# First we drop all traffic on the old interface.
# Then we try to add the ip to the new interface and before
# we finally remove it from the old interface.
# Moving an IP is a bit more complex than it seems. First we
# drop all traffic on the old interface. Then we try to
# remove the IP from the old interface and add it to the new
# interface.
#
# The steps are:
#
# 1) firewall this IP, so no new external packets arrive for it
# 2) remove the IP from the old interface (and new interface, to be sure)
# 3) add the IP to the new interface
# 4) remove the firewall rule
# 5) use ctdb gratarp to propagate the new mac address
# 6) use netstat -tn to find existing connections, and tickle them
# 6) send tickle ACKs for existing connections, so dropped
# packets are resent
_oiface=$2
niface=$3
_ip=$4
@ -226,10 +230,10 @@ updateip)
flush_route_cache
# propagate the new mac address
# Propagate the new MAC address
$CTDB gratarp "$ip" "$niface"
# tickle all existing connections, so that dropped packets
# Tickle all existing connections, so that dropped packets
# are retransmitted and the tcp streams work
tickle_tcp_connections "$ip"
;;

5
ctdb/doc/ctdb-script.options.5.xml
View File

@ -105,8 +105,9 @@
<title>10.interface</title>
<para>
This event script handles monitoring of interfaces using by
public IP addresses.
This event script handles public IP address release and
takeover, as well as monitoring interfaces used by public IP
addresses.
</para>
<variablelist>