Restore functionality of route-gateway's dhcp parameter

PATCH New James Bekkema 1 participant 1 message Jul 23, 2018

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James Bekkema

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2018-07-23 03:45 UTC #0 lore raw

PATCH 1/1 Restore functionality of route-gateway's dhcp parameter

This patch restores functionality of route-gateway's dhcp parameter, and expands it to support routes using vpn_gateway.

OpenVPN supports using a “dhcp” parameter for the "route-gateway” option, which involves intercepting the DHCP reply packet and extracting the gateway to use. However, the current implementation expects to have this information at the time of the initialisation of the route list, which will not happen, and so routes relying on this option are never added.

Rather than moving initialisation of the route list until after the route-delay (which can have a negative effect on the resolution of routes using FQDNs), this patch flags routes that require a DHCP gateway, and updates and defines them when a DHCP reply is received. If no reply is received in time, the routes are left undefined.

Currently in production use in Viscosity for macOS and Windows, no reported issues.

Signed-off-by James Bekkema <[email protected]...>

Thanks,
James

--
James Bekkema
SparkLabs Developer
https://www.sparklabs.com
https://twitter.com/sparklabs
[email protected]...

From 363ad7103507bcc092fde61c3b60bd3cfbf60aaa Mon Sep 17 00:00:00 2001
From: James Bekkema <[email protected]...>
Date: Mon, 23 Jul 2018 13:21:53 +1000
Subject: [PATCH] Restore functionality of route-gateway's dhcp parameter, and
expand to support routes using vpn_gateway.

---
 src/openvpn/init.c  |  1 +
 src/openvpn/route.c | 32 ++++++++++++++++++++++++++++++--
 src/openvpn/route.h |  3 +++
 3 files changed, 34 insertions(+), 2 deletions(-)

src/openvpn/init.c +1 -0

index d28d1fd2..057dbb4b 100644
@@ -1396,6 +1396,7 @@ do_init_route_list(const struct options *options,
     if (init_route_list(route_list,
                         options->routes,
                         gw,
+                        options->route_gateway_via_dhcp,
                         metric,
                         link_socket_current_remote(link_socket_info),
                         es))

src/openvpn/route.c +30 -2

index ff392308..ad8ea135 100644
@@ -295,6 +295,12 @@ is_special_addr(const char *addr_str)
     }
 }
 
+static bool
+should_use_dhcp_gateway(const char *gateway, const struct route_list *rl)
+{
+    return (rl->spec.flags & RTSA_DHCP_ENDPOINT && (!is_route_parm_defined(gateway) || !strcmp(gateway, "vpn_gateway")));
+}
+
 static bool
 init_route(struct route_ipv4 *r,
            struct addrinfo **network_list,

@@ -362,7 +368,11 @@ init_route(struct route_ipv4 *r,
 
     /* gateway */
 
-    if (is_route_parm_defined(ro->gateway))
+    if (should_use_dhcp_gateway(ro->gateway, rl))
+    {
+        r->flags |= RT_DHCP_GATEWAY;
+    }
+    else if (is_route_parm_defined(ro->gateway))
     {
         if (!get_special_addr(rl, ro->gateway, &r->gateway, &status))
         {

@@ -414,7 +424,10 @@ init_route(struct route_ipv4 *r,
         r->flags |= RT_METRIC_DEFINED;
     }
 
-    r->flags |= RT_DEFINED;
+    if ((r->flags & RT_DHCP_GATEWAY) == 0)
+    {
+        r->flags |= RT_DEFINED;
+    }
 
     return true;

@@ -541,6 +554,16 @@ route_list_add_vpn_gateway(struct route_list *rl,
     rl->spec.remote_endpoint = addr;
     rl->spec.flags |= RTSA_REMOTE_ENDPOINT;
     setenv_route_addr(es, "vpn_gateway", rl->spec.remote_endpoint, -1);
+
+    struct route_ipv4 *r;
+    for (r = rl->routes; r; r = r->next)
+    {
+        if (r->flags & RT_DHCP_GATEWAY)
+        {
+            r->gateway = addr;
+            r->flags |= RT_DEFINED;
+        }
+    }
 }
 
 static void

@@ -611,6 +634,7 @@ bool
 init_route_list(struct route_list *rl,
                 const struct route_option_list *opt,
                 const char *remote_endpoint,
+                bool remote_endpoint_dhcp,
                 int default_metric,
                 in_addr_t remote_host,
                 struct env_set *es)

@@ -676,6 +700,10 @@ init_route_list(struct route_list *rl,
             ret = false;
         }
     }
+    else if (remote_endpoint_dhcp)
+    {
+        rl->spec.flags |= RTSA_DHCP_ENDPOINT;
+    }
 
     if (rl->flags & RG_ENABLE)
     {

src/openvpn/route.h +3 -0

index 69420228..948c892e 100644
@@ -62,6 +62,7 @@ struct route_special_addr
 #define RTSA_REMOTE_ENDPOINT  (1<<0)
 #define RTSA_REMOTE_HOST      (1<<1)
 #define RTSA_DEFAULT_METRIC   (1<<2)
+#define RTSA_DHCP_ENDPOINT    (1<<3)
     unsigned int flags;
 
     in_addr_t remote_endpoint;

@@ -112,6 +113,7 @@ struct route_ipv4 {
 #define RT_DEFINED        (1<<0)
 #define RT_ADDED          (1<<1)
 #define RT_METRIC_DEFINED (1<<2)
+#define RT_DHCP_GATEWAY   (1<<3)
     struct route_ipv4 *next;
     unsigned int flags;
     const struct route_option *option;

@@ -280,6 +282,7 @@ void add_route_ipv6_to_option_list(struct route_ipv6_option_list *l,
 bool init_route_list(struct route_list *rl,
                      const struct route_option_list *opt,
                      const char *remote_endpoint,
+                     bool remote_endpoint_dhcp,
                      int default_metric,
                      in_addr_t remote_host,
                      struct env_set *es);

Signature · 1 line

2.17.1