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Date: Tue, 20 Apr 2021 01:22:41 +0300
From: Alexey Kondratov <a.kondratov@postgrespro.ru>
To: pgsql-hackers@lists.postgresql.org
Subject: Free port choosing freezes when PostgresNode::use_tcp is used on BSD
 systems
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Hi Hackers,

Inside PostgresNode.pm there is a free port choosing routine --- 
get_free_port(). The comment section there says:

	# On non-Linux, non-Windows kernels, binding to 127.0.0/24 addresses
	# other than 127.0.0.1 might fail with EADDRNOTAVAIL.

And this is an absolute true, on BSD-like systems (macOS and FreeBSD 
tested) it hangs on looping through the entire ports range over and over 
when $PostgresNode::use_tcp = 1 is set, since bind fails with:

# Checking port 52208
# bind: 127.0.0.1 52208
# bind: 127.0.0.2 52208
bind: Can't assign requested address

To reproduce just apply reproduce.diff and try to run 'make -C 
src/bin/pg_ctl check'.

This is not a case with standard Postgres tests, since TestLib.pm 
chooses unix sockets automatically everywhere outside Windows. However, 
we got into this problem when tried to run a custom tap test that 
required TCP for stable running.

That way, if it really could happen why not to just skip binding to 
127.0.0/24 addresses other than 127.0.0.1 outside of Linux/Windows as 
per attached patch_PostgresNode.diff?


Regards
-- 
Alexey Kondratov

Postgres Professional https://www.postgrespro.com
Russian Postgres Company
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