PHP5 - Fails to resolve hostnames when not in interactive mode

Question

I'm working with an OS X 10.6 Server running Apache2 / PHP5 and having a problem with PHP not resolving hostnames when 'fopen()' tries to retrieve a file from a remote server. When run in interactive mode on the command line 'fopen()' works perfectly. However, when run through the web it will always fail with the error:

failed to open stream: php_network_getaddresses: getaddrinfo failed: nodename nor servname provided, or not known

I'm at a loss in finding the source of this problem: 'fopen()' works on the web when given an IP address instead of a hostname; 'gethostbyname()' also fails when run on the web (it doesn't error, it just returns whatever hostname it was given to resolve) but also works fine when run in interactive mode. The only exception seems to be 'dns_get_record()' which works fine when run on the web or in interactive mode.

I've been trying to find DNS problems on the server but dig, nslookup, and ping all work and "scutil -r" says the remote server is reachable with the current DNS settings. Any ideas on where the problem might be?

Solution 1

Try to recompile PHP with '--disable-ipv6' option. Then, apachectl stop & start (not 'apachectl restart'). I've got the same error message on Mac OS 10.6.4 + manually compiled PHP5.3.3 + Apache2.2.16.

Solution 2

You must set properly the allow_url_fopen value of your php.ini.

http://ar.php.net/manual/en/filesystem.configuration.php#ini.allow-url-fopen

Consider the CLI uses a different php.ini that the webserver (I assume you are using Apache).

Another option may be you are not including libnss_dns

Try adding to your httpd configuration (correct path as needed for you system):

LoadFile /lib/libnss_dns.so

Solution 3

If you are are running PHP-FPM with chroot settings (as you should be) - then neither DNS nor mail will work.

---

Update Feb 2016

strace using gethostbyname only from the test-script @ https://knzl.de/setting-up-a-chroot-for-php/ solved dns for me in an Alpine Linux / nginx chroot. I also use the sh from this link with mini-sendmail to solve the mail problem.

---

An approximate list of files needed for DNS & Mail in a chroot

The following commands got DNS working for me with PHP5.5 on Debian (tested with the Joomla builtin update component):

#!/bin/sh

chroot=/var/www
domain=mydomain
webuser=www-data
webgroup=www-data

cd $chroot/$domain

mkdir etc

cp /etc/resolv.conf etc/
cp /etc/nsswitch.conf etc/
echo $(cat /etc/group|grep $webgroup) > etc/group
echo $(cat /etc/passwd|grep $webuser) > etc/passwd
cp /etc/services etc/
cp /etc/protocols etc/
cp /etc/host.conf etc/
cp /etc/hosts etc/
cp /etc/networks etc/

mkdir -p usr/bin   
mkdir usr/sbin

cp /usr/sbin/ssmtp usr/sbin/
cp /usr/sbin/sendmail usr/sbin/

mkdir usr/share

cp -rf /usr/share/zoneinfo usr/share

mkdir lib

cp /lib/i386-linux-gnu/libresolv.so.2 lib/
cp /lib/i386-linux-gnu/libnss_compat.so.2 lib/
cp /lib/i386-linux-gnu/libc.so.6 lib/
cp /lib/i386-linux-gnu/libnsl.so.1 lib/
cp /lib/i386-linux-gnu/libnss_files.so.2 lib/
cp /lib/i386-linux-gnu/libz.so.1 lib/
cp /lib/i386-linux-gnu/libdl.so.2 lib/
cp /lib/i386-linux-gnu/libcidn.so.1 lib/
cp /lib/i386-linux-gnu/ld-linux.so.2 lib/
cp /lib/i386-linux-gnu/libcrypt.so.1 lib/
cp /lib/i386-linux-gnu/libnss_nis.so.2 lib/
cp /lib/i386-linux-gnu/libnss_dns.so.2 lib/

chown -R $webuser:$webgroup lib usr etc
service php5-fpm restart

I did not need /bin/sh or /usr/lib/locale

Solution 4

Same problem, different solution then the original poster. I was calling mysqli(...) to connect, but the URL I had for the server was wrong. So it doesn't always mean you are unable to do any DNS lookup, just that the server that it is not able to do that specific lookup (check your host!)

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Comments

[Pekka]

I don't think allow_url_fopen() is the problem here, but comparing the PHP.ini's is a good idea.

[Kaja]

Apologies, I should have explicitly stated that I'd checked the PHP.ini in use by Apache to be certain allow_url_fopen() was on. I'm looking into 'libnss_dns.so' but I've been unable to locate it in OS X 10.6 or the MacPorts distribution of Apache2. I didn't think it important when first posting, but this problem first occurred a few months ago and I was able to work around it by adding the remote server to '/etc/hosts'. Whatever the problem is now, manually editing the 'hosts' file doesn't seem to help.

[richardkmiller]

I was also getting this error with MacPorts 1.9.1. Installing ldns (sudo port install ldns) fixed it for me.

[Derek Downey]

I know this is old, but I was having this exact problem and removing ipv6 support fixed it for me

[Marcel Colomb]

sudo port install ldns and restarting Apache fixed the problem for me as well thx!

[Flexo]

It would be a better idea to fix the underlying problem than just brushing it under the carpet like that.

[nortron]

The LoadFile directive fixed my problem, I couldn't get DNS resolution to work through Apache but it would work on the CLI.

[BadPirate]

This is a gotcha listed in the PHP mysqli command (localhost is magic, so you need to use the IP 127.0.0.1 when trying to connect to it directly)

[jakabadambalazs]

Yes, this work for me as well (i also have libnss_dns.so.2 and libnss_files.so.2) - I think if you look into your [chroot]/usr/share/zoneinfo you'll have a missing symlink to /etc/localtime (it seems missing from your procedure) - i think it is needed

[jakabadambalazs]

You do not need the curl binary in your chrooted environment to be able to use php cURL. As a matter of fact, Joomla updates even without the php5-curl package installed. But if you need it and you install it, it works perfectly without the curl binary(and its libraries) in the chroot.

[Stuart Cardall]

@jakabadambalazs - yes curl binary not needed - have added an update to the instructions with my current method.

[TheDudeAbides]

@richardkmiller But how on earth did you determine that ldns was necessary? (I should note that this did did solve my problem with PHP 5.6.20 from MacPorts on OS X 10.11, while I was testing with the boris REPL.)

[richardkmiller]

@TheDudeAbides I wish I could remember. It has been too long and now I'm using brew.