freebsd stable - Jun 2018 - syslogd became silent between 11.2-PRERELEASE r334874 and r335282

On 17. Jun 2018, at 16:27, Michael Grimm <trashcan at ellael.org> wrote:
> Hi,
> 
> I am running service jails (VNET/bridge/epair) and a host at
11.2-PRERELEASE r335282, upgraded from r334874 today.
> 
> All syslog messages at each jail become forwarded to syslogd running at the
host. This setup worked for years. Today not a single syslog message becomes
forwarded to the host's syslogd.
I do believe that this commit might be the cause: 
https://svnweb.freebsd.org/base/stable/11/usr.sbin/syslogd/Makefile?revision=335059&view=markup&sortby=file

But I do have to admit, that I do not understand what changed and what would
cause my syslogd become silenced, though.

Any hints?
> 
> Host's syslogd can be reached from inside every jail, e.g.:
> 
> 	jtest> nc -4vuw 1 10.x.y.z 514 
> 	Connection to 10.x.y.z 514 port [udp/syslog] succeeded!
> 
> logger doesn't throw any error. No message will be forwarded to the
host's syslogd either:
> 
> 	jtest> logger -4 10.x.y.z HELLO
> 	jtest>
> 
> I cannot find any hint in src/UPDATING. 
> 
> What did I miss?
> Anyone else with a silenced syslogd?
> Anyone running my setup with a noisy syslogd?
> 
> Thank you in advance and regards,
> Michael
> 
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Hi Michael,

2018-06-17 17:52 GMT+02:00 Michael Grimm <trashcan at
ellael.org>:
> I do believe that this commit might be the cause:
>
https://svnweb.freebsd.org/base/stable/11/usr.sbin/syslogd/Makefile?revision=335059&view=markup&sortby=file
Thanks for reporting this issue. I just did some debugging on my
system and I think I was able to reproduce this issue. It seems as if
I made a tiny mistake in how I implemented the RFC 5426 UDP message
size limiting. Could you please give the following patch for syslogd a
try?

Index: usr.sbin/syslogd/syslogd.c
==================================================================---
usr.sbin/syslogd/syslogd.c  (revision 334706)
+++ usr.sbin/syslogd/syslogd.c  (working copy)
@@ -1613,8 +1613,8 @@
        struct iovec *last;
        size_t diff;

-       while (size > il->totalsize) {
-               diff = size - il->totalsize;
+       while (il->totalsize > size) {
+               diff = il->totalsize - size;
                last = &il->iov[il->iovcnt - 1];
                if (diff >= last->iov_len) {
                        /* Remove the last iovec entirely. */

It should be sufficient to apply this to just the 'client' syslogd.
There is no need to patch the central (storage) server.

-- 
Ed Schouten <ed at nuxi.nl>
Nuxi, 's-Hertogenbosch, the Netherlands