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From 222bce6b83421db1afdad24cf4e8ab7b1aa7b273 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Tue, 18 Jan 2022 14:48:33 +0100
Subject: [PATCH] server/sockets: get rid of AI_ADDRCONFIG
The AI_ADDRCONFIG hint of getaddrinfo() is supposed to restrict the name
resolution to such address families (IPv4 vs. IPv6) for which the
resolving host has publicly routable addresses assigned.
The main problem with AI_ADDRCONFIG can be shown with the following
command line:
$ nbdkit -f -p 32776 -P pidfile -i ::1 --exit-with-parent null
On a host where ::1 is the only IPv6 address assigned (namely to the
loopback interface), the command fails with
> nbdkit: getaddrinfo: ::1: 32776: Address family for hostname not
> supported
due to the "publicly routable" requirement.
Remove AI_ADDRCONFIG from the getaddrinfo() hints, and as a replacement,
introduce the "-4" and "-6" options, similarly to netcat and ssh.
(1) This makes options of the form:
-i 127.0.0.1
-i ::1
work regardless of "public" IPv6 / IPv4 connectivity;
(2) options of the form
-i localhost
-i FQDN
will bind both IPv4 and IPv6 addresses of the desired interface(s);
(3) omitting the option "-i" will bind both IPv4 and IPv6 wildcard
addresses (0.0.0.0 and ::);
(4) the configurations in (2) and (3) can be restricted to IPv4 or IPv6
addresses by adding the "-4" or "-6" option, respectively.
Importantly, this change allows the "connect-tcp6" test case of libnbd to
pass on such hosts that have no IPv6 connectivity (i.e., where the only
assigned IPv6 address is ::1, namely on the loopback interface).
Ref: https://listman.redhat.com/archives/libguestfs/2022-January/msg00110.html
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20220118134833.13246-3-lersek@redhat.com>
[lersek@redhat.com: fix typo in "--exit-with-parent" (Eric)]
Acked-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 9eec2335d630ae8ef947a927c1922d725d482f4a)
---
common/utils/windows-compat.h | 7 -------
docs/nbdkit.pod | 20 +++++++++++++++++++-
docs/synopsis.txt | 3 ++-
server/internal.h | 1 +
server/main.c | 9 +++++++++
server/options.h | 4 +++-
server/sockets.c | 3 ++-
7 files changed, 36 insertions(+), 11 deletions(-)
diff --git a/common/utils/windows-compat.h b/common/utils/windows-compat.h
index 7695bf7e..658c1d8b 100644
--- a/common/utils/windows-compat.h
+++ b/common/utils/windows-compat.h
@@ -75,13 +75,6 @@ struct sockaddr_un
#define O_NOCTTY 0
#endif
-/* AI_ADDRCONFIG is not available on Windows. It enables a rather
- * obscure feature of getaddrinfo to do with IPv6.
- */
-#ifndef AI_ADDRCONFIG
-#define AI_ADDRCONFIG 0
-#endif
-
/* Windows <errno.h> lacks certain errnos, so replace them here as
* best we can.
*/
diff --git a/docs/nbdkit.pod b/docs/nbdkit.pod
index 99cfb362..042607fb 100644
--- a/docs/nbdkit.pod
+++ b/docs/nbdkit.pod
@@ -173,6 +173,24 @@ Display information about nbdkit or a specific plugin:
Display brief command line usage information and exit.
+=item B<-4>
+
+=item B<--ipv4-only>
+
+=item B<-6>
+
+=item B<--ipv6-only>
+
+When a non-numeric argument is passed to the I<-i> option (such as a
+Fully Qualified Domain Name, or a host name from C</etc/hosts>),
+restrict the name resolution to IPv4 or IPv6 addresses.
+
+When the I<-i> option is omitted, listen on only the IPv4 or IPv6
+address of all interfaces (C<0.0.0.0> or C<::>, respectively).
+
+When both I<-4> and I<-6> options are present on the command line, the
+last one takes effect.
+
=item B<-D> PLUGIN.FLAG=N
=item B<-D> FILTER.FLAG=N
@@ -265,7 +283,7 @@ See also I<-u>.
=item B<--ipaddr> IPADDR
Listen on the specified interface. The default is to listen on all
-interfaces. See also I<-p>.
+interfaces. See also I<-4>, I<-6>, and I<-p>.
=item B<--log=stderr>
diff --git a/docs/synopsis.txt b/docs/synopsis.txt
index 07b9dcff..6154bb2e 100644
--- a/docs/synopsis.txt
+++ b/docs/synopsis.txt
@@ -1,4 +1,5 @@
-nbdkit [-D|--debug PLUGIN|FILTER|nbdkit.FLAG=N]
+nbdkit [-4|--ipv4-only] [-6|--ipv6-only]
+ [-D|--debug PLUGIN|FILTER|nbdkit.FLAG=N]
[-e|--exportname EXPORTNAME] [--exit-with-parent]
[--filter FILTER ...] [-f|--foreground]
[-g|--group GROUP] [-i|--ipaddr IPADDR]
diff --git a/server/internal.h b/server/internal.h
index bc81b786..46fcdd46 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -113,6 +113,7 @@ enum log_to {
LOG_TO_NULL, /* --log=null forced on the command line */
};
+extern int tcpip_sock_af;
extern struct debug_flag *debug_flags;
extern const char *export_name;
extern bool foreground;
diff --git a/server/main.c b/server/main.c
index 225258de..8e7ac149 100644
--- a/server/main.c
+++ b/server/main.c
@@ -86,6 +86,7 @@ static void error_if_stdio_closed (void);
static void switch_stdio (void);
static void winsock_init (void);
+int tcpip_sock_af = AF_UNSPEC; /* -4, -6 */
struct debug_flag *debug_flags; /* -D */
bool exit_with_parent; /* --exit-with-parent */
const char *export_name; /* -e */
@@ -367,6 +368,14 @@ main (int argc, char *argv[])
exit (EXIT_FAILURE);
#endif
+ case '4':
+ tcpip_sock_af = AF_INET;
+ break;
+
+ case '6':
+ tcpip_sock_af = AF_INET6;
+ break;
+
case 'D':
add_debug_flag (optarg);
break;
diff --git a/server/options.h b/server/options.h
index e59ef17f..39299b9d 100644
--- a/server/options.h
+++ b/server/options.h
@@ -59,8 +59,10 @@ enum {
VSOCK_OPTION,
};
-static const char *short_options = "D:e:fg:i:nop:P:rst:u:U:vV";
+static const char *short_options = "46D:e:fg:i:nop:P:rst:u:U:vV";
static const struct option long_options[] = {
+ { "ipv4-only", no_argument, NULL, '4' },
+ { "ipv6-only", no_argument, NULL, '6' },
{ "debug", required_argument, NULL, 'D' },
{ "dump-config", no_argument, NULL, DUMP_CONFIG_OPTION },
{ "dump-plugin", no_argument, NULL, DUMP_PLUGIN_OPTION },
diff --git a/server/sockets.c b/server/sockets.c
index 15a26f69..4e4ccbc4 100644
--- a/server/sockets.c
+++ b/server/sockets.c
@@ -179,7 +179,8 @@ bind_tcpip_socket (sockets *socks)
port = "10809";
memset (&hints, 0, sizeof hints);
- hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
+ hints.ai_flags = AI_PASSIVE;
+ hints.ai_family = tcpip_sock_af;
hints.ai_socktype = SOCK_STREAM;
err = getaddrinfo (ipaddr, port, &hints, &ai);
--
2.31.1
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