Handle missing DCO peer by restarting the session

Occasionally, CMD_DEL_PEER is not delivered to userspace, preventing the
openvpn process from registering the event. To handle this case, we
check if calls to the Linux DCO module return an error, and, if so, send
a SIGUSR1 signal to reset the session.

Most DCO commands that return an error already trigger a SIGUSR1 signal
or even call _exit(1). This commit extends that behavior to include
dco_get_peer_stats_multi() and dco_get_peer_stats().

Change-Id: Ib118426c5a69256894040c69856a4003d9f4637c
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20250305171730.250444-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg31022.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

src/openvpn/dco.h

@@ -231,17 +231,20 @@ void dco_delete_iroutes(struct multi_context *m, struct multi_instance *mi);
 /**
  * Update traffic statistics for all peers
  *
- * @param dco   DCO device context
- * @param m     the server context
+ * @param dco                   DCO device context
+ * @param m                     the server context
+ * @param raise_sigusr1_on_err  whether to raise SIGUSR1 on error
  **/
-int dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m);
+int dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m,
+                             const bool raise_sigusr1_on_err);
 
 /**
  * Update traffic statistics for single peer
  *
- * @param c   instance context of the peer
+ * @param c                     instance context of the peer
+ * @param raise_sigusr1_on_err  whether to raise SIGUSR1 on error
  **/
-int dco_get_peer_stats(struct context *c);
+int dco_get_peer_stats(struct context *c, const bool raise_sigusr1_on_err);
 
 /**
  * Retrieve the list of ciphers supported by the current platform
@@ -373,13 +376,14 @@ dco_delete_iroutes(struct multi_context *m, struct multi_instance *mi)
 }
 
 static inline int
-dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m)
+dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m,
+                         const bool raise_sigusr1_on_err)
 {
     return 0;
 }
 
 static inline int
-dco_get_peer_stats(struct context *c)
+dco_get_peer_stats(struct context *c, const bool raise_sigusr1_on_err)
 {
     return 0;
 }

src/openvpn/dco_freebsd.c

@@ -713,7 +713,8 @@ dco_update_peer_stat(struct multi_context *m, uint32_t peerid, const nvlist_t *n
 }
 
 int
-dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m)
+dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m,
+                         const bool raise_sigusr1_on_err)
 {
 
     struct ifdrv drv;
@@ -781,7 +782,7 @@ retry:
 }
 
 int
-dco_get_peer_stats(struct context *c)
+dco_get_peer_stats(struct context *c, const bool raise_sigusr1_on_err)
 {
     /* Not implemented. */
     return 0;

src/openvpn/dco_linux.c

@@ -952,7 +952,8 @@ dco_parse_peer_multi(struct nl_msg *msg, void *arg)
 }
 
 int
-dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m)
+dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m,
+                         const bool raise_sigusr1_on_err)
 {
     msg(D_DCO_DEBUG, "%s", __func__);
 
@@ -963,6 +964,14 @@ dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m)
     int ret = ovpn_nl_msg_send(dco, nl_msg, dco_parse_peer_multi, m, __func__);
 
     nlmsg_free(nl_msg);
+
+    if (raise_sigusr1_on_err && ret < 0)
+    {
+        msg(M_WARN, "Error retrieving DCO peer stats: the underlying DCO peer"
+            "may have been deleted from the kernel without notifying "
+            "userspace. Restarting the session");
+        register_signal(m->top.sig, SIGUSR1, "dco peer stats error");
+    }
     return ret;
 }
 
@@ -1008,9 +1017,14 @@ dco_parse_peer(struct nl_msg *msg, void *arg)
 }
 
 int
-dco_get_peer_stats(struct context *c)
+dco_get_peer_stats(struct context *c, const bool raise_sigusr1_on_err)
 {
-    uint32_t peer_id = c->c2.tls_multi->dco_peer_id;
+    int peer_id = c->c2.tls_multi->dco_peer_id;
+    if (peer_id == -1)
+    {
+        return 0;
+    }
+
     msg(D_DCO_DEBUG, "%s: peer-id %d", __func__, peer_id);
 
     if (!c->c1.tuntap)
@@ -1030,6 +1044,14 @@ dco_get_peer_stats(struct context *c)
 
 nla_put_failure:
     nlmsg_free(nl_msg);
+
+    if (raise_sigusr1_on_err && ret < 0)
+    {
+        msg(M_WARN, "Error retrieving DCO peer stats: the underlying DCO peer"
+            "may have been deleted from the kernel without notifying "
+            "userspace. Restarting the session");
+        register_signal(c->sig, SIGUSR1, "dco peer stats error");
+    }
     return ret;
 }
 

src/openvpn/dco_win.c

@@ -712,14 +712,15 @@ dco_do_read(dco_context_t *dco)
 }
 
 int
-dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m)
+dco_get_peer_stats_multi(dco_context_t *dco, struct multi_context *m,
+                         const bool raise_sigusr1_on_err)
 {
     /* Not implemented. */
     return 0;
 }
 
 int
-dco_get_peer_stats(struct context *c)
+dco_get_peer_stats(struct context *c, const bool raise_sigusr1_on_err)
 {
     struct tuntap *tt = c->c1.tuntap;
 

src/openvpn/forward.c

@@ -488,7 +488,7 @@ check_add_routes(struct context *c)
 static void
 check_inactivity_timeout(struct context *c)
 {
-    if (dco_enabled(&c->options) && dco_get_peer_stats(c) == 0)
+    if (dco_enabled(&c->options) && dco_get_peer_stats(c, true) == 0)
     {
         int64_t tot_bytes = c->c2.tun_read_bytes + c->c2.tun_write_bytes;
         int64_t new_bytes = tot_bytes - c->c2.inactivity_bytes;
@@ -497,7 +497,6 @@ check_inactivity_timeout(struct context *c)
         {
             c->c2.inactivity_bytes = tot_bytes;
             event_timeout_reset(&c->c2.inactivity_interval);
-
             return;
         }
     }

src/openvpn/manage.c

@@ -4146,8 +4146,13 @@ management_check_bytecount(struct context *c, struct management *man, struct tim
         counter_type dco_read_bytes = 0;
         counter_type dco_write_bytes = 0;
 
-        if (dco_enabled(&c->options) && (dco_get_peer_stats(c) == 0))
+        if (dco_enabled(&c->options))
         {
+            if (dco_get_peer_stats(c, true) < 0)
+            {
+                return;
+            }
+
             dco_read_bytes = c->c2.dco_read_bytes;
             dco_write_bytes = c->c2.dco_write_bytes;
         }
@@ -4166,7 +4171,8 @@ management_check_bytecount(struct context *c, struct management *man, struct tim
 void
 man_persist_client_stats(struct management *man, struct context *c)
 {
-    if (dco_enabled(&c->options) && (dco_get_peer_stats(c) == 0))
+    /* no need to raise SIGUSR1 since we are already closing the instance */
+    if (dco_enabled(&c->options) && (dco_get_peer_stats(c, false) == 0))
     {
         management_bytes_client(man, c->c2.dco_read_bytes, c->c2.dco_write_bytes);
     }

src/openvpn/multi.c

@@ -548,7 +548,10 @@ setenv_stats(struct multi_context *m, struct context *c)
 {
     if (dco_enabled(&m->top.options))
     {
-        dco_get_peer_stats_multi(&m->top.c1.tuntap->dco, m);
+        if (dco_get_peer_stats_multi(&m->top.c1.tuntap->dco, m, false) < 0)
+        {
+            return;
+        }
     }
 
     setenv_counter(c->c2.es, "bytes_received", c->c2.link_read_bytes + c->c2.dco_read_bytes);
@@ -856,7 +859,10 @@ multi_print_status(struct multi_context *m, struct status_output *so, const int
 
         if (dco_enabled(&m->top.options))
         {
-            dco_get_peer_stats_multi(&m->top.c1.tuntap->dco, m);
+            if (dco_get_peer_stats_multi(&m->top.c1.tuntap->dco, m, true) < 0)
+            {
+                return;
+            }
         }
 
         if (version == 1)

src/openvpn/sig.c

@@ -489,7 +489,10 @@ print_status(struct context *c, struct status_output *so)
 
     if (dco_enabled(&c->options))
     {
-        dco_get_peer_stats(c);
+        if (dco_get_peer_stats(c, true) < 0)
+        {
+            return;
+        }
     }
 
     status_printf(so, "OpenVPN STATISTICS");