[pve-devel] [RFC common/manger] use appropriate wildcard address for pveproxy/spiceproxy

[pve-devel] [RFC common/manger] use appropriate wildcard address for pveproxy/spiceproxy

[Stoiko Ivanov]

The following patchset tries to address the small regression reported in our
forums [0,1], resulting from defaulting to '::' as listen-address in
pveproxy/spiceproxy.

The issue also affects proxmox-backup-proxy in PBS - and should this approach
be accepted I'll try to port it over to PBS as well.
(ftr: pmgproxy was not affected, since the patch for pmg-api was not applied)

In all cases the issue is only exhibited if ipv6 is diabled via kernel
commandline [2], not via sysctl [3].

* The patchset keeps the fix for pveproxy not starting if the /etc/hosts entry
  is not matching with a configured IP-address (I noticed and was pleasantly
  surprised while testing a v6only host and forgetting to set the entry)

I tested it in the following scenarios:
* ipv6 disabled via kernel commandline (listen on 0.0.0.0)
* ipv6 disabled via sysctl (listen on 0.0.0.0)
* no settings dual-stacked (listen on *)
* no settings v6 only (listen on *)

AFAICT listening on :: as long as possible is the best option, since it
makes the service available on all address-families (doing away, with
having a v4 only /etc/hosts entry, but a DNS AAAA record pointing to
the node for external access).

Took a quick look at how sshd [4,5] handles this (in the assumption that
they have to get it as right as possible), but it listens on multiple
sockets, something which I'd like to avoid for our proxy-daemons.

Sending as RFC, because whenever I come near getaddrinfo/getnameinfo I'm
certain to miss quite a few common cases.

[0] https://forum.proxmox.com/threads/connection-refused-595-nach-update-auf-pve-6-4.88347/#post-387034
[1] https://forum.proxmox.com/threads/ipv6-komplett-deaktivieren.88210/#post-387116
[2] https://www.kernel.org/doc/html/latest/networking/ipv6.html
[3] https://www.kernel.org/doc/html/latest/networking/ip-sysctl.html
[4] https://github.com/openssh/openssh-portable/blob/master/servconf.c
[5] https://github.com/openssh/openssh-portable/blob/master/sshd.c

pve-common:
Stoiko Ivanov (1):
  tools: add get_wildcard_address

 src/PVE/Tools.pm | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

pve-manager:
Stoiko Ivanov (1):
  proxy: fix wildcard address use

 PVE/Service/pveproxy.pm   | 2 +-
 PVE/Service/spiceproxy.pm | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

-- 
2.20.1

[pve-devel] [RFC common 1/1] tools: add get_wildcard_address

[Stoiko Ivanov]

the get_wildcard_address sub returns the appropriate wildcard address:
* '::' if the hosts has any v6 address (including link-local scoped)
  configured (i.e. default behavior without any modification to sysctl
  or kernel commandline)
* '0.0.0.0' if ipv6 is disabled via sysctl or kernel commandline

This should ensure the best behaviour for listening sockets in
dual-stacked environments:
* binding to '::' allows to connect via both v6 and v4 addresses (the
  latter are treated as v4-mapped-v6 addresses (::ffff:192.0.2.1))
* the current unconditional bind to '::' fails if AF_INET6 is not
  supported via kernel commandline setting [0].
* the previous approach of finding the family based on the node-name
  getaddrinfo result leads to the service only being available on v4
  despite having a working v6 address configured, in case it's
  /etc/hosts entry points only to the v4 address.

[0] on linux passing ipv6.disable=1 on the kernel commandline removes
support for AF_INET6 sockets (setting the net.ipv6.conf.*.disable_ipv6
sysctls keeps support)

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
 src/PVE/Tools.pm | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/PVE/Tools.pm b/src/PVE/Tools.pm
index 16ae3d2..fb520ce 100644
--- a/src/PVE/Tools.pm
+++ b/src/PVE/Tools.pm
@@ -4,8 +4,8 @@ use strict;
 use warnings;
 use POSIX qw(EINTR EEXIST EOPNOTSUPP);
 use IO::Socket::IP;
-use Socket qw(AF_INET AF_INET6 AI_ALL AI_V4MAPPED AI_CANONNAME SOCK_DGRAM
-	      IPPROTO_TCP);
+use Socket qw(AF_INET AF_INET6 AI_ALL AI_V4MAPPED AI_CANONNAME AI_PASSIVE
+	    AI_ADDRCONFIG NI_NUMERICHOST NI_NUMERICSERV SOCK_DGRAM IPPROTO_TCP);
 use IO::Select;
 use File::Basename;
 use File::Path qw(make_path);
@@ -1405,6 +1405,24 @@ sub get_host_address_family {
     return $res[0]->{family};
 }
 
+# returns "::" if the host supports AF_INET6 else "0.0.0.0"
+sub get_wildcard_address {
+    my %hints = (
+	flags => AI_PASSIVE|AI_ADDRCONFIG,
+    );
+    my ($err, @res) = Socket::getaddrinfo('', '0', \%hints);
+    die "failed to get address info for wildcard address: $err\n" if $err;
+
+    my $sockaddr = $res[0]->{addr};
+    if (my @v6support = grep {$_->{family} eq AF_INET6} @res) {;
+	$sockaddr = $v6support[0]->{addr};
+    }
+    my $host;
+    ($err, $host) = Socket::getnameinfo($sockaddr, NI_NUMERICHOST|NI_NUMERICSERV);
+    die "failed to get name info for wildcard address: $err\n" if $err;
+    return $host;
+}
+
 # get the fully qualified domain name of a host
 # same logic as hostname(1): The FQDN is the name getaddrinfo(3) returns,
 # given a nodename as a parameter
-- 
2.20.1

[pve-devel] [RFC manager 1/1] proxy: fix wildcard address use

[Stoiko Ivanov]

This patch fixes a regression for hosts disabling ipv6 via kernel
commandline ('ipv6.disable=1')introduced in commit
fc087ec2b924dc9c72d3bf80face8a1731c15405

by hardcoding the address to '::', pveproxy and spiceproxy failed to
start with:
'unable to create socket - Address family not supported by protocol'

Disabling IPv6 via sysctl did not exhibit these problems.

This patch depends on the commit in pve-common and needs a versioned
dependency bump on libpve-common-perl.

With this patch the listening addresses are (`ss -tlnp |grep 8006` output)
* disabled via kernel cmdline: '0.0.0.0:8006'
* disabled via sysctl net.ipv6.conf.all.disable_ipv6=1: '0.0.0.0:8006'
* else: '*:8006'

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
 PVE/Service/pveproxy.pm   | 2 +-
 PVE/Service/spiceproxy.pm | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/PVE/Service/pveproxy.pm b/PVE/Service/pveproxy.pm
index 4ecd442a..742c0a9a 100755
--- a/PVE/Service/pveproxy.pm
+++ b/PVE/Service/pveproxy.pm
@@ -69,7 +69,7 @@ sub init {
     my $lockfh = IO::File->new(">>${accept_lock_fn}") ||
 	die "unable to open lock file '${accept_lock_fn}' - $!\n";
 
-    my $listen_ip = $proxyconf->{LISTEN_IP} // "::0";
+    my $listen_ip = $proxyconf->{LISTEN_IP} // PVE::Tools::get_wildcard_address();
     my $socket = $self->create_reusable_socket(8006, $listen_ip);
 
     my $dirs = {};
diff --git a/PVE/Service/spiceproxy.pm b/PVE/Service/spiceproxy.pm
index 24be0ed7..34882ca4 100755
--- a/PVE/Service/spiceproxy.pm
+++ b/PVE/Service/spiceproxy.pm
@@ -39,7 +39,7 @@ sub init {
     my $lockfh = IO::File->new(">>${accept_lock_fn}") ||
 	die "unable to open lock file '${accept_lock_fn}' - $!\n";
 
-    my $listen_ip = $proxyconf->{LISTEN_IP} // "::0";
+    my $listen_ip = $proxyconf->{LISTEN_IP} // PVE::Tools::get_wildcard_address();
     my $socket = $self->create_reusable_socket(3128, $listen_ip);
 
     $self->{server_config} = {
-- 
2.20.1

Re: [pve-devel] [RFC manager 1/1] proxy: fix wildcard address use

[Wolfgang Bumiller]

On Thu, Apr 29, 2021 at 03:37:02PM +0200, Stoiko Ivanov wrote:
> This patch fixes a regression for hosts disabling ipv6 via kernel
> commandline ('ipv6.disable=1')introduced in commit
> fc087ec2b924dc9c72d3bf80face8a1731c15405
> 
> by hardcoding the address to '::', pveproxy and spiceproxy failed to
> start with:
> 'unable to create socket - Address family not supported by protocol'
> 
> Disabling IPv6 via sysctl did not exhibit these problems.
> 
> This patch depends on the commit in pve-common and needs a versioned
> dependency bump on libpve-common-perl.
> 
> With this patch the listening addresses are (`ss -tlnp |grep 8006` output)
> * disabled via kernel cmdline: '0.0.0.0:8006'
> * disabled via sysctl net.ipv6.conf.all.disable_ipv6=1: '0.0.0.0:8006'
> * else: '*:8006'
> 
> Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
> ---
>  PVE/Service/pveproxy.pm   | 2 +-
>  PVE/Service/spiceproxy.pm | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/PVE/Service/pveproxy.pm b/PVE/Service/pveproxy.pm
> index 4ecd442a..742c0a9a 100755
> --- a/PVE/Service/pveproxy.pm
> +++ b/PVE/Service/pveproxy.pm
> @@ -69,7 +69,7 @@ sub init {
>      my $lockfh = IO::File->new(">>${accept_lock_fn}") ||
>  	die "unable to open lock file '${accept_lock_fn}' - $!\n";
>  
> -    my $listen_ip = $proxyconf->{LISTEN_IP} // "::0";
> +    my $listen_ip = $proxyconf->{LISTEN_IP} // PVE::Tools::get_wildcard_address();
>      my $socket = $self->create_reusable_socket(8006, $listen_ip);

^ This passes `Domain => PF_INET6`. That makes no sense given that I can
literally give it an IPv4 :S

It also actually uses getaddrinfo in the background, however, the
commmit forcing this to be 0 explains:

    perl's IO::Socket::IP passes AI_ADDRCONFIG if no GetAddrInfoFlags are passed,
    which is often useful but also causes it to error when explicitly trying to
    bind to 127.0.0.1 when there are no _other_ IPv4 addresses present.

In this case however, we don't do that, so maybe instead of ending up using
`getaddrinfo` twice, we should just make this an optional parameter?
I'm hoping passing `undef` as host, the proper port and `AI_ADDRCONFIG |
AI_PASSIVE` here should do the same?

We also don't use `$listen_ip` for anything else either, so we don't need it
explicitly ;-)

>  
>      my $dirs = {};
> diff --git a/PVE/Service/spiceproxy.pm b/PVE/Service/spiceproxy.pm
> index 24be0ed7..34882ca4 100755
> --- a/PVE/Service/spiceproxy.pm
> +++ b/PVE/Service/spiceproxy.pm
> @@ -39,7 +39,7 @@ sub init {
>      my $lockfh = IO::File->new(">>${accept_lock_fn}") ||
>  	die "unable to open lock file '${accept_lock_fn}' - $!\n";
>  
> -    my $listen_ip = $proxyconf->{LISTEN_IP} // "::0";
> +    my $listen_ip = $proxyconf->{LISTEN_IP} // PVE::Tools::get_wildcard_address();
>      my $socket = $self->create_reusable_socket(3128, $listen_ip);
>  
>      $self->{server_config} = {
> -- 
> 2.20.1