[Openvpn-devel,S] Change in openvpn[master]: options: add IPv4 support to '--show-gateway <arg>'

Message ID d2c88065fbe966e93f5c1752fa4eb9f438d9b227-HTML@gerrit.openvpn.net
State Superseded
Headers show
Series [Openvpn-devel,S] Change in openvpn[master]: options: add IPv4 support to '--show-gateway <arg>' | expand

Commit Message

cron2 (Code Review) Jan. 29, 2025, 11:30 a.m. UTC
Attention is currently required from: flichtenheld, plaisthos.

Hello plaisthos, flichtenheld,

I'd like you to do a code review.
Please visit

    http://gerrit.openvpn.net/c/openvpn/+/881?usp=email

to review the following change.


Change subject: options: add IPv4 support to '--show-gateway <arg>'
......................................................................

options: add IPv4 support to '--show-gateway <arg>'

This is an old debug option, which used to print "the default routes found"
for IPv4 and IPv6, and optionally "a route to a particular IPv6 target"
if passed an argument.

With the work started in commit 0fcfc8381f60d we want this to handle
IPv4 as well, mostly to be able to easily test per-platform
get_default_gateway() implementations.

The implementation is simplistic - if <arg> can be parsed as an IPv4 or
IPv6 address, that particular protocol lookup will do "the host route"
and the other one will stick to "the default route".

Change-Id: Ic438c583a782035ecb9b5ea65702a768ae2585f5
Signed-off-by: Gert Doering <gert@greenie.muc.de>
---
M doc/man-sections/advanced-options.rst
M src/openvpn/options.c
2 files changed, 18 insertions(+), 8 deletions(-)



  git pull ssh://gerrit.openvpn.net:29418/openvpn refs/changes/81/881/1

Patch

diff --git a/doc/man-sections/advanced-options.rst b/doc/man-sections/advanced-options.rst
index d5a6b4f..e1115e4 100644
--- a/doc/man-sections/advanced-options.rst
+++ b/doc/man-sections/advanced-options.rst
@@ -9,13 +9,17 @@ 
   ::
 
      --show-gateway
+     --show-gateway IPv4-target
      --show-gateway IPv6-target
 
+  For IPv4 it looks for a 0.0.0.0/0 route, or the specified IPv4 address
+  if the target can be parsed as an IPv4 address.
   For IPv6 this queries the route towards ::/128, or the specified IPv6
-  target address if passed as argument.
-  For IPv4 on Linux, Windows, MacOS and BSD it looks for a 0.0.0.0/0 route.
-  If there are more specific routes, the result will not always be matching
-  the route of the IPv4 packets to the VPN gateway.
+  target address if the argument is an IPv6 address.
+
+  Adding a target is helpful for diagnostics to see if OpenVPN will do
+  the right thing if there are more specific IPv4/IPv6 routes to a
+  VPN server.
 
 
 Advanced Expert Options
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index 5a80e6b..2897961 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -5858,16 +5858,22 @@ 
     {
         struct route_gateway_info rgi;
         struct route_ipv6_gateway_info rgi6;
-        struct in6_addr remote = IN6ADDR_ANY_INIT;
+        in_addr_t remote_ipv4 = 0;
+        struct in6_addr remote_ipv6 = IN6ADDR_ANY_INIT;
         openvpn_net_ctx_t net_ctx;
         VERIFY_PERMISSION(OPT_P_GENERAL);
         if (p[1])
         {
-            get_ipv6_addr(p[1], &remote, NULL, M_WARN);
+            /* try parsing the argument as a v4 or v6 address - if
+             * possible, the output will show the exact route there, and
+             * "the default route" for the other protocol
+             */
+            remote_ipv4 = get_ip_addr(p[1], M_WARN, NULL);
+            get_ipv6_addr(p[1], &remote_ipv6, NULL, M_WARN);
         }
         net_ctx_init(NULL, &net_ctx);
-        get_default_gateway(&rgi, 0, &net_ctx);
-        get_default_gateway_ipv6(&rgi6, &remote, &net_ctx);
+        get_default_gateway(&rgi, remote_ipv4, &net_ctx);
+        get_default_gateway_ipv6(&rgi6, &remote_ipv6, &net_ctx);
         print_default_gateway(M_INFO, &rgi, &rgi6);
         openvpn_exit(OPENVPN_EXIT_STATUS_GOOD); /* exit point */
     }