Hi,

for the netlink/sitnl bits: this makes sense to me.
I agree with Selva that the v6 variant could benefit from the same treatment.

However, this patch can also be hacked on its own

Acked-by: Antonio Quartulli <a...@unstable.cc>

On 11/01/2023 17:08, Gert Doering wrote:
The code in sitnl_route_set() used to treat "route can not be installed
because it already exists" (EEXIST) as "not an error".

This is arguably a reasonable approach, but needs to handled higher
up - if the low level add_route() function say "no error", we will try
to remove that route later on in delete_route(), possibly removing
someone else's "already existing" route then.

So:
  - remove special case in sitnl_route_set()
  - do not pass NLM_F_REPLACE flag to sitnl_route_set() call - this would
    cause netlink to just replace existing routes, never return EEXIST
    (see "man netlink(7)")
  - add detailed return code handling to route_add(), assign "2" on "-EEXIST"
    (and log appropriate message).

(Note: sitnl_route_set() is a common function for sitnl route add and
delete, but EEXIST can not happen on delete - so this change has no
impact for the "delete" case)

Signed-off-by: Gert Doering <g...@greenie.muc.de>
---
  src/openvpn/networking_sitnl.c |  6 +-----
  src/openvpn/route.c            | 10 ++++++++--
  2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/openvpn/networking_sitnl.c b/src/openvpn/networking_sitnl.c
index fe124616..92f30044 100644
--- a/src/openvpn/networking_sitnl.c
+++ b/src/openvpn/networking_sitnl.c
@@ -944,10 +944,6 @@ sitnl_route_set(int cmd, uint32_t flags, int ifindex, 
sa_family_t af_family,
      }
ret = sitnl_send(&req.n, 0, 0, NULL, NULL);
-    if (ret == -EEXIST)
-    {
-        ret = 0;
-    }
  err:
      return ret;
  }
@@ -1177,7 +1173,7 @@ sitnl_route_add(const char *iface, sa_family_t af_family, 
const void *dst,
          scope = RT_SCOPE_LINK;
      }
- return sitnl_route_set(RTM_NEWROUTE, NLM_F_CREATE | NLM_F_REPLACE, ifindex,
+    return sitnl_route_set(RTM_NEWROUTE, NLM_F_CREATE, ifindex,
                             af_family, dst, prefixlen, gw, table, metric, 
scope,
                             RTPROT_BOOT, RTN_UNICAST);
  }
diff --git a/src/openvpn/route.c b/src/openvpn/route.c
index 99f948ba..2db127bb 100644
--- a/src/openvpn/route.c
+++ b/src/openvpn/route.c
@@ -1594,8 +1594,14 @@ add_route(struct route_ipv4 *r,
      }
status = 1;
-    if (net_route_v4_add(ctx, &r->network, netmask_to_netbits2(r->netmask),
-                         &r->gateway, iface, 0, metric) < 0)
+    int ret = net_route_v4_add(ctx, &r->network, 
netmask_to_netbits2(r->netmask),
+                               &r->gateway, iface, 0, metric);
+    if (ret == -EEXIST)
+    {
+        msg(D_ROUTE, "NOTE: Linux route add command failed because route 
exists");
+        status = 2;
+    }
+    else if (ret < 0)
      {
          msg(M_WARN, "ERROR: Linux route add command failed");
          status = 0;

--
Antonio Quartulli


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