[syslog-ng] "Syslog connection closed" but socket not closed

[Patrick Hemmer]

We recently saw an issue where syslog-ng (version 3.6.4 on FreeBSD 10.1) 
was configured with a `syslog()` source, received an invalid frame, shut 
down the connection, but the socket remained open. I was looking through 
the documented fixes in the versions since the one we're using (3.6.4), 
but nothing looks related.

2016-01-21T07:44:21-05:00 iad1gweb01.ecom.chewy.com     ERR 
syslog-ng[27090]: - Invalid frame header; header='' [meta sequenceId="389"]
2016-01-21T07:44:21-05:00 iad1gweb01.ecom.chewy.com  NOTICE 
syslog-ng[27090]: - Syslog connection closed; fd='19', 
client='AF_INET(127.0.0.1:59317)', local='AF_INET(127.0.0.1:601)' [meta 
sequenceId="390"]

# netstat -an|grep 59317
tcp4   81660      0 127.0.0.1.601 127.0.0.1.59317        ESTABLISHED
tcp4       0  48923 127.0.0.1.59317 127.0.0.1.601          ESTABLISHED

 From the netstat output (the buffer sizes), it looks like syslog-ng 
stopped reading from the socket, but didn't close it, and the 
application on the other end kept trying to write to it.

This is just my theory anyway. I can open a bug on github, but I wanted 
to bring it up here first.

Thanks

-Patrick