[M] Change in openvpn[master]: Add support for user defined L3 master devices

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Hello plaisthos,

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

    http://gerrit.openvpn.net/c/openvpn/+/1703?usp=email

to review the following change.


Change subject: Add support for user defined L3 master devices
......................................................................

Add support for user defined L3 master devices

Introduce the --l3mdev option to allow associating OpenVPN
tun interfaces with a user-defined L3 master device (VRF).

When configured, the tun interface is automatically bound
to the specified l3mdev during interface initialization.

This allows VPN traffic to operate within a VRF domain,
enabling network isolation and policy-based routing at L3 level.

Note: This feature is Linux-only and relies on SITNL backend.

Change-Id: I115a17a2c61c65f48aea41d94150f34ea31f82da
Signed-off-by: Gianmarco De Gregori <[email protected]>
---
M doc/man-sections/vpn-network-options.rst
M src/openvpn/dco.c
M src/openvpn/networking.h
M src/openvpn/networking_sitnl.c
M src/openvpn/networking_sitnl.h
M src/openvpn/options.c
M src/openvpn/options.h
M src/openvpn/tun.c
8 files changed, 95 insertions(+), 0 deletions(-)



  git pull ssh://gerrit.openvpn.net:29418/openvpn refs/changes/03/1703/1

diff --git a/doc/man-sections/vpn-network-options.rst b/doc/man-sections/vpn-network-options.rst
index 181c990..4cc11e9 100644
--- a/doc/man-sections/vpn-network-options.rst
+++ b/doc/man-sections/vpn-network-options.rst
@@ -304,6 +304,12 @@
   Specify the link layer address, more commonly known as the MAC address.
   Only applied to TAP devices.
 
+--l3mdev name
+   Specify the L3 master device (such as VRF) to which the tunnel 
+   interface will be bound. The specified device must already exist.
+
+  (Supported on Linux only, on other platforms this is a no-op).
+
 --netns name
   Specify the network namespace in which the tunnel interface will be created.
   The namespace must already exist.
diff --git a/src/openvpn/dco.c b/src/openvpn/dco.c
index fbefcb6..40ef5b6 100644
--- a/src/openvpn/dco.c
+++ b/src/openvpn/dco.c
@@ -395,6 +395,7 @@
         msg(msglevel, "Note: --netns not supported by DCO, disabling data channel offload.");
         return false;
     }
+
 #endif /* if defined(_WIN32) */
 
 #if defined(HAVE_LIBCAPNG)
diff --git a/src/openvpn/networking.h b/src/openvpn/networking.h
index fab6bbf..3b4ac9f 100644
--- a/src/openvpn/networking.h
+++ b/src/openvpn/networking.h
@@ -125,6 +125,16 @@
 int net_iface_del(openvpn_net_ctx_t *ctx, const openvpn_net_iface_t *iface);
 
 /**
+ * Bind a network interface to an L3 master device.
+ *
+ * @param ctx       OpenVPN network context.
+ * @param iface     Interface to bind.
+ *
+ * @return 0 on success, -1 on error.
+ */
+int net_iface_l3mdev_bind(openvpn_net_ctx_t *ctx, const char *iface);
+
+/**
  * Bring interface up or down.
  *
  * @param ctx       the implementation specific context
diff --git a/src/openvpn/networking_sitnl.c b/src/openvpn/networking_sitnl.c
index b60131f..bb9e77a 100644
--- a/src/openvpn/networking_sitnl.c
+++ b/src/openvpn/networking_sitnl.c
@@ -187,6 +187,7 @@
     char path[PATH_MAX];
 
     ctx->netns = NULL;
+    ctx->l3mdev = NULL;
 
     if (c && c->options.netns)
     {
@@ -200,6 +201,16 @@
         ctx->netns = c->options.netns;
     }
 
+    if (c && c->options.l3mdev)
+    {
+        if (!if_nametoindex(c->options.l3mdev))
+        {
+            msg(M_ERR, "%s: L3 master device %s does not exist", __func__, c->options.l3mdev);
+        }
+
+        ctx->l3mdev = c->options.l3mdev;
+    }
+
     ctx->gc = gc_new();
     return 0;
 }
@@ -1046,6 +1057,44 @@
 #ifdef ENABLE_SITNL
 
 int
+net_iface_l3mdev_bind(openvpn_net_ctx_t *ctx, const char *iface)
+{
+    struct sitnl_link_req req;
+    int ifindex, l3mdev_index, ret = -1;
+
+    CLEAR(req);
+
+    ifindex = if_nametoindex(iface);
+    l3mdev_index = if_nametoindex(ctx->l3mdev);
+
+    if (ifindex == 0)
+    {
+        msg(M_WARN | M_ERRNO, "%s: rtnl: cannot get ifindex for %s", __func__, iface);
+        return -1;
+    }
+    if (l3mdev_index == 0)
+    {
+        msg(M_WARN | M_ERRNO, "%s: rtnl: cannot get ifindex for %s", __func__, ctx->l3mdev);
+        return -1;
+    }
+
+    req.n.nlmsg_len = NLMSG_LENGTH(sizeof(req.i));
+    req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+    req.n.nlmsg_type = RTM_NEWLINK;
+
+    req.i.ifi_family = AF_PACKET;
+    req.i.ifi_index = ifindex;
+
+    SITNL_ADDATTR(&req.n, sizeof(req), IFLA_MASTER, &l3mdev_index, sizeof(int));
+
+    msg(M_INFO, "Binding %s to %s", iface, ctx->l3mdev);
+
+    ret = sitnl_send(&req.n, 0, 0, NULL, NULL);
+err:
+    return ret;
+}
+
+int
 net_iface_up(openvpn_net_ctx_t *ctx, const char *iface, bool up)
 {
     struct sitnl_link_req req;
diff --git a/src/openvpn/networking_sitnl.h b/src/openvpn/networking_sitnl.h
index 7e723fe..6dff698 100644
--- a/src/openvpn/networking_sitnl.h
+++ b/src/openvpn/networking_sitnl.h
@@ -28,6 +28,7 @@
 struct openvpn_net_ctx
 {
     const char *netns;
+    const char *l3mdev;
     struct gc_arena gc;
 };
 
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index bde3680..5247c8e 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -6496,6 +6496,14 @@
         VERIFY_PERMISSION(OPT_P_GENERAL);
         options->netns = p[1];
     }
+    else if (streq(p[0], "l3mdev") && p[1] && !p[2])
+    {
+#ifndef ENABLE_SITNL
+        msg(M_WARN, "NOTE: --l3mdev is supported only on Linux when compiled with SITNL");
+#endif
+        VERIFY_PERMISSION(OPT_P_GENERAL);
+        options->l3mdev = p[1];
+    }
     else if (streq(p[0], "nice") && p[1] && !p[2])
     {
         VERIFY_PERMISSION(OPT_P_NICE);
diff --git a/src/openvpn/options.h b/src/openvpn/options.h
index 88a6dfa..1afd41b 100644
--- a/src/openvpn/options.h
+++ b/src/openvpn/options.h
@@ -316,6 +316,7 @@
     struct dns_options dns_options;
 
     const char *netns;
+    const char *l3mdev;
     bool remote_random;
     const char *ipchange;
     const char *dev;
diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c
index 51d9bed..250ce50 100644
--- a/src/openvpn/tun.c
+++ b/src/openvpn/tun.c
@@ -1059,6 +1059,15 @@
     {
         msg(M_FATAL, "Linux can't set mtu (%d) on %s", tun_mtu, ifname);
     }
+#if defined(ENABLE_SITNL)
+    if (ctx->l3mdev)
+    {
+        if (net_iface_l3mdev_bind(ctx, ifname) < 0)
+        {
+            msg(M_NONFATAL, "Linux can't bind %s to %s", ifname, ctx->l3mdev);
+        }
+    }
+#endif
 
     if (net_iface_up(ctx, ifname, true) < 0)
     {
@@ -1265,6 +1274,16 @@
         msg(M_FATAL, "Linux can't set mtu (%d) on %s", tun_mtu, ifname);
     }
 
+#if defined(ENABLE_SITNL)
+    if (ctx->l3mdev)
+    {
+        if (net_iface_l3mdev_bind(ctx, ifname) < 0)
+        {
+            msg(M_NONFATAL, "Linux can't bind %s to %s", ifname, ctx->l3mdev);
+        }
+    }
+#endif
+
     if (net_iface_up(ctx, ifname, true) < 0)
     {
         msg(M_FATAL, "Linux can't bring %s up", ifname);

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Gerrit-MessageType: newchange
Gerrit-Project: openvpn
Gerrit-Branch: master
Gerrit-Change-Id: I115a17a2c61c65f48aea41d94150f34ea31f82da
Gerrit-Change-Number: 1703
Gerrit-PatchSet: 1
Gerrit-Owner: its_Giaan <[email protected]>
Gerrit-Reviewer: plaisthos <[email protected]>
Gerrit-CC: openvpn-devel <[email protected]>
Gerrit-Attention: plaisthos <[email protected]>

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