[Babel-users] [OpenWrt-Devel] [PATCH] babeld: use procd to start, stop, and respawn

Mon Sep 8 17:54:29 UTC 2014

On Mon, Sep 8, 2014 at 6:10 AM, Baptiste Jonglez <bjonglez at illyse.org> wrote:
> Hi,
>
> Note that babeld is maintained in https://github.com/openwrt-routing/packages.
> Nevertheless, comments inline.
>
> On Sun, Sep 07, 2014 at 05:56:32PM -0400, Tristan Plumb wrote:
>> Changes the babeld init script to utilize procd and
>
> Nice, it was a requested feature:
>
>   https://github.com/openwrt-routing/packages/issues/17
>
> Could you separate your patch into three patches? (procd support, hotplug
> script, pidfile hack)
>
>> adds a hotplug.d file to restart babeld when interfaces go up or down.
>
> Somebody provided a patch for this just a few days ago, see:
>
>   https://github.com/openwrt-routing/packages/pull/52
>
> However, see the comments: this should not be needed, as babeld detects
> when an interface is brought up and then starts using it.  What is your
> use-case?
>
>> Additionally adds a patch to the babeld source is to prevent the
>> attempted recreation of a pidfile when babeld restarts uncleanly. This is
>> also possible to do by passing -I '' on the command line, however procd
>> interprets an empty argument terminating the list, and thus cannot supply
>> empty arguments to programs it manages.

> Patching babeld itself is a workaround.  Why not tackle the root issue?
> It seems that you encountered crashes in babeld, so that should be fixed,
> instead of working around the crashes.  I did experience a few babeld
> crashes myself, but never managed to find where they came from.

There lies the rub. If you have a deployed machine on a rooftop somewhere,
it is better to restart the daemon automagically and log the action
rather than attempt to
debug it. Using procd to manage this stuff reduces the probability of a babel
failure taking out a node by several orders of magnitude, and I strongly favor
managing it this way. Certainly finding and fixing bugs so that it doesn't
ever crash is a good option, but in the real world, nothing is perfect, and
defense in depth is needed.
>
>> Signed-off-by: Tristan Plumb <tristan at trstn.net>
>> ---
>> diff --git a/babeld/Makefile b/babeld/Makefile
>> index e939310..70fcd64 100644
>> --- a/babeld/Makefile
>> +++ b/babeld/Makefile
>> @@ -54,6 +54,8 @@ define Package/babeld/install
>>       $(INSTALL_CONF) ./files/babeld.config $(1)/etc/config/babeld
>>       $(INSTALL_DIR) $(1)/etc/init.d
>>       $(INSTALL_BIN) ./files/babeld.init $(1)/etc/init.d/babeld
>> +     $(INSTALL_DIR) $(1)/etc/hotplug.d/iface
>> +     $(INSTALL_DATA) ./files/babeld.hotplug $(1)/etc/hotplug.d/iface/25-babeld
>>  endef
>>
>>  $(eval $(call BuildPackage,babeld))
>> diff --git a/babeld/files/babeld.hotplug b/babeld/files/babeld.hotplug
>> new file mode 100644
>> index 0000000..3fe674a
>> --- /dev/null
>> +++ b/babeld/files/babeld.hotplug
>> @@ -0,0 +1,6 @@
>> +#!/bin/sh
>> +
>> +[ "$ACTION" = ifup ] || exit 0
>> +
>> +/etc/init.d/babeld enabled && /etc/init.d/babeld restart
>> +
>> diff --git a/babeld/files/babeld.init b/babeld/files/babeld.init
>> index 180fc7e..de8d73b 100755
>> --- a/babeld/files/babeld.init
>> +++ b/babeld/files/babeld.init
>> @@ -2,9 +2,9 @@
>>
>>  . /lib/functions/network.sh
>>
>> +USE_PROCD=1
>>  START=70
>>
>> -pidfile='/var/run/babeld.pid'
>>  CONFIGFILE='/var/etc/babeld.conf'
>>  OTHERCONFIGFILE="/etc/babeld.conf"
>>  EXTRA_COMMANDS="status"
>> @@ -197,7 +197,7 @@ babel_config_cb() {
>>       esac
>>  }
>>
>> -start() {
>> +start_service() {
>>       mkdir -p /var/lib
>>       # Start by emptying the generated config file
>>       >"$CONFIGFILE"
>> @@ -213,26 +213,17 @@ start() {
>>       config_foreach parse_old_global_options general
>>       # Parse filters separately, since we know which options we expect
>>       config_foreach babel_filter filter
>> +     procd_open_instance
>>       # Using multiple config files is supported since babeld 1.5.1
>> -     /usr/sbin/babeld -D -I "$pidfile" -c "$OTHERCONFIGFILE" -c "$CONFIGFILE"
>> -     # Wait for the pidfile to appear
>> -     for i in 1 2
>> -     do
>> -             [ -f "$pidfile" ] || sleep 1
>> -     done
>> -     [ -f "$pidfile" ] || (echo "Failed to start babeld"; exit 42)
>> +     procd_set_param command /usr/sbin/babeld -c "$OTHERCONFIGFILE" -c "$CONFIGFILE"
>> +     procd_set_param respawn
>> +     procd_close_instance
>>  }
>>
>> -stop() {
>> -     [ -f "$pidfile" ] && kill $(cat $pidfile)
>> -  # avoid race-condition on restart: wait for
>> -  # babeld to die for real.
>> -  [ -f "$pidfile" ] && sleep 1
>> -  [ -f "$pidfile" ] && sleep 1
>> -  [ -f "$pidfile" ] && sleep 1
>> -  [ -f "$pidfile" ] && exit 42
>> +service_triggers() {
>> +     procd_add_reload_trigger babeld
>>  }
>>
>>  status() {
>> -     [ -f "$pidfile" ] && kill -USR1 $(cat $pidfile)
>> +     kill -USR1 $(pidof babeld)
>>  }
>> diff --git a/babeld/patches/001-no-default-pidfile.patch b/babeld/patches/001-no-default-pidfile.patch
>> new file mode 100644
>> index 0000000..74ac6b4
>> --- /dev/null
>> +++ b/babeld/patches/001-no-default-pidfile.patch
>> @@ -0,0 +1,21 @@
>> +diff --git a/babeld.c b/babeld.c
>> +index 656c9da..88e4aec 100644
>> +--- a/babeld.c
>> ++++ b/babeld.c
>> +@@ -66,7 +66,7 @@ int resend_delay = -1;
>> + int random_id = 0;
>> + int do_daemonise = 0;
>> + const char *logfile = NULL,
>> +-    *pidfile = "/var/run/babeld.pid",
>> ++    *pidfile = NULL,
>> +     *state_file = "/var/lib/babel-state";
>> +
>> + unsigned char *receive_buffer = NULL;
>> +@@ -251,6 +251,7 @@ main(int argc, char **argv)
>> +             break;
>> +         case 'D':
>> +             do_daemonise = 1;
>> ++            pidfile = "/var/run/babeld.pid";
>> +             break;
>> +         case 'L':
>> +             logfile = optarg;
>
> _______________________________________________
> Babel-users mailing list
> Babel-users at lists.alioth.debian.org
> http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/babel-users


-- 
Dave Täht

https://www.bufferbloat.net/projects/make-wifi-fast