Added default gateway support to the routing table reachability check

src/ucs/sys/netlink.c

@@ -29,6 +29,8 @@ typedef struct {
     const struct sockaddr *sa_remote;
     int                    if_index;
     int                    found;
+    int                    allow_default_gw; /* Allow matching default
+                                                gateway routes */
 } ucs_netlink_route_info_t;
 
 
@@ -174,7 +176,7 @@ ucs_netlink_send_request(int protocol, unsigned short nlmsg_type,
 
 static ucs_status_t
 ucs_netlink_get_route_info(const struct rtattr *rta, int len, int *if_index_p,
-                           const void **dst_in_addr)
+                           const void **dst_in_addr, unsigned char rtm_dst_len)
 {
     *if_index_p  = -1;
     *dst_in_addr = NULL;
@@ -187,7 +189,8 @@ ucs_netlink_get_route_info(const struct rtattr *rta, int len, int *if_index_p,
         }
     }
 
-    if ((*if_index_p == -1) || (*dst_in_addr == NULL)) {
+    /* dst_in_addr is required only for non-default gateway routes */
+    if ((*if_index_p == -1) || ((*dst_in_addr == NULL) && (rtm_dst_len != 0))) {
         return UCS_ERR_INVALID_PARAM;
     }
 
@@ -206,7 +209,8 @@ ucs_netlink_parse_rt_entry_cb(const struct nlmsghdr *nlh, void *arg)
     int khret;
 
     if (ucs_netlink_get_route_info(RTM_RTA(rt_msg), RTM_PAYLOAD(nlh),
-                                   &iface_index, &dst_in_addr) != UCS_OK) {
+                                   &iface_index, &dst_in_addr,
+                                   rt_msg->rtm_dst_len) != UCS_OK) {
         return UCS_INPROGRESS;
     }
 
@@ -228,12 +232,14 @@ ucs_netlink_parse_rt_entry_cb(const struct nlmsghdr *nlh, void *arg)
                                 ucs_error("could not allocate route entry");
                                 return UCS_ERR_NO_MEMORY);
 
-    memset(&new_rule->dest, 0, sizeof(sizeof(new_rule->dest)));
+    memset(&new_rule->dest, 0, sizeof(new_rule->dest));
     new_rule->dest.ss_family = rt_msg->rtm_family;
-    if (UCS_OK != ucs_sockaddr_set_inet_addr((struct sockaddr *)&new_rule->dest,
-                                             dst_in_addr)) {
-        ucs_array_pop_back(iface_rules);
-        return UCS_ERR_IO_ERROR;
+    if (dst_in_addr != NULL) {
+        if (ucs_sockaddr_set_inet_addr((struct sockaddr *)&new_rule->dest,
+                                       dst_in_addr) != UCS_OK) {
+            ucs_array_pop_back(iface_rules);
+            return UCS_ERR_IO_ERROR;
+        }
     }
 
     new_rule->subnet_prefix_len = rt_msg->rtm_dst_len;
@@ -256,6 +262,15 @@ static void ucs_netlink_lookup_route(ucs_netlink_route_info_t *info)
 
     iface_rules = &kh_val(&ucs_netlink_routing_table_cache, iter);
     ucs_array_for_each(curr_entry, iface_rules) {
+
+        /* Skip default gateway routes if not allowed (e.g., for
+           IPoIB remote devices) */
+        if ((curr_entry->subnet_prefix_len == 0) && !info->allow_default_gw) {
+            ucs_trace("iface_index=%d: skipping default gateway route",
+                      info->if_index);
+            continue;
+        }
+
         if (ucs_sockaddr_is_same_subnet(
                                 info->sa_remote,
                                 (const struct sockaddr *)&curr_entry->dest,
@@ -266,7 +281,8 @@ static void ucs_netlink_lookup_route(ucs_netlink_route_info_t *info)
     }
 }
 
-int ucs_netlink_route_exists(int if_index, const struct sockaddr *sa_remote)
+int ucs_netlink_route_exists(int if_index, const struct sockaddr *sa_remote,
+                             int allow_default_gw)
 {
     static ucs_init_once_t init_once = UCS_INIT_ONCE_INITIALIZER;
     struct rtmsg rtm                 = {0};
@@ -285,9 +301,11 @@ int ucs_netlink_route_exists(int if_index, const struct sockaddr *sa_remote)
                                  NULL);
     }
 
-    info.if_index  = if_index;
-    info.sa_remote = sa_remote;
-    info.found     = 0;
+    info.if_index         = if_index;
+    info.sa_remote        = sa_remote;
+    info.found            = 0;
+    info.allow_default_gw = allow_default_gw;
+
     ucs_netlink_lookup_route(&info);
 
     return info.found;

src/ucs/sys/netlink.h

@@ -48,14 +48,17 @@ ucs_netlink_send_request(int protocol, unsigned short nlmsg_type,
  * Check whether a routing table rule exists for a given network
  * interface name and a destination address.
  *
- * @param [in]  if_index   A global index representing the network interface,
-                           as assigned by the system (e.g., obtained via
-                           if_nametoindex()).
- * @param [in]  sa_remote  Pointer to the destination address.
+ * @param [in]  if_index          A global index representing the network
+                                  interface, as assigned by the system
+                                  (e.g., obtained via if_nametoindex()).
+ * @param [in]  sa_remote         Pointer to the destination address.
+ * @param [in]  allow_default_gw  Allow matching default gateway routes (1) or
+ *                                only specific subnet routes (0).
  *
  * @return 1 if rule exists, or 0 otherwise.
  */
-int ucs_netlink_route_exists(int if_index, const struct sockaddr *sa_remote);
+int ucs_netlink_route_exists(int if_index, const struct sockaddr *sa_remote,
+                             int allow_default_gw);
 
 END_C_DECLS
 

src/ucs/sys/sys.c

@@ -15,6 +15,7 @@
 #include <ucs/sys/checker.h>
 #include <ucs/sys/ptr_arith.h>
 #include <ucs/sys/string.h>
+#include <ucs/sys/sock.h>
 #include <ucs/sys/sys.h>
 #include <ucs/debug/log.h>
 #include <ucs/time/time.h>
@@ -177,6 +178,21 @@ ucs_status_t ucs_ifname_to_index(const char *ndev_name, unsigned *ndev_index_p)
     return UCS_OK;
 }
 
+int ucs_netif_is_ipoib(const char *if_name)
+{
+    struct ifreq ifr;
+    ucs_status_t status;
+
+    status = ucs_netif_ioctl(if_name, SIOCGIFHWADDR, &ifr);
+    if (status != UCS_OK) {
+        /* If we can't determine the hardware type, assume it's not IPoIB */
+        ucs_debug("failed to get hardware address for %s", if_name);
+        return 0;
+    }
+
+    return ifr.ifr_hwaddr.sa_family == ARPHRD_INFINIBAND;
+}
+
 static uint64_t ucs_get_mac_address()
 {
     static uint64_t mac_address = 0;

src/ucs/sys/sys.h

@@ -192,6 +192,16 @@ uint32_t ucs_file_checksum(const char *filename);
 ucs_status_t ucs_ifname_to_index(const char *ndev_name, unsigned *ndev_index_p);
 
 
+/**
+ * Check if a network interface is an IPoIB (IP over InfiniBand) device.
+ *
+ * @param [in]  if_name  Network interface name to check.
+ *
+ * @return 1 if the interface is IPoIB, 0 otherwise.
+ */
+int ucs_netif_is_ipoib(const char *if_name);
+
+
 /**
  * Get a globally unique identifier of the machine running the current process.
  */

src/uct/ib/base/ib_iface.c

@@ -710,7 +710,7 @@ uct_ib_iface_roce_is_routable(uct_ib_iface_t *iface, uint8_t gid_index,
         return 0;
     }
 
-    if (!ucs_netlink_route_exists(ndev_index, sa_remote)) {
+    if (!ucs_netlink_route_exists(ndev_index, sa_remote, 1)) {
         /* try to use loopback interface for reachability check, because it may
          * be used for routing in case of an interface with VRF is configured
          * and a RoCE IP interface uses this VRF table for routing.
@@ -721,7 +721,7 @@ uct_ib_iface_roce_is_routable(uct_ib_iface_t *iface, uint8_t gid_index,
             return 0;
         }
 
-        if (!ucs_netlink_route_exists(lo_ndev_index, sa_remote)) {
+        if (!ucs_netlink_route_exists(lo_ndev_index, sa_remote, 1)) {
             uct_iface_fill_info_str_buf(params,
                                         "remote address %s is not routable "
                                         "neither by interface "UCT_IB_IFACE_FMT

src/uct/tcp/tcp.h

@@ -295,7 +295,12 @@ typedef enum uct_tcp_device_addr_flags {
      * Device address is extended by additional information:
      * @ref uct_iface_local_addr_ns_t for loopback reachability
      */
-    UCT_TCP_DEVICE_ADDR_FLAG_LOOPBACK = UCS_BIT(0)
+    UCT_TCP_DEVICE_ADDR_FLAG_LOOPBACK         = UCS_BIT(0),
+
+    /**
+     * Allow communication with default gateway
+     */
+    UCT_TCP_DEVICE_ADDR_FLAG_ALLOW_DEFAULT_GW = UCS_BIT(1)
 } uct_tcp_device_addr_flags_t;
 
 

src/uct/tcp/tcp_iface.c

@@ -13,6 +13,7 @@
 #include <ucs/async/async.h>
 #include <ucs/sys/netlink.h>
 #include <ucs/sys/string.h>
+#include <ucs/sys/sys.h>
 #include <ucs/config/types.h>
 #include <sys/socket.h>
 #include <sys/poll.h>
@@ -138,6 +139,11 @@ static ucs_status_t uct_tcp_iface_get_device_address(uct_iface_h tl_iface,
     dev_addr->flags     = 0;
     dev_addr->sa_family = saddr->sa_family;
 
+    /* Default gateway is not relevant for IPoIB interfaces */
+    if (!ucs_netif_is_ipoib(iface->if_name)) {
+        dev_addr->flags |= UCT_TCP_DEVICE_ADDR_FLAG_ALLOW_DEFAULT_GW;
+    }
+
     if (ucs_sockaddr_is_inaddr_loopback(saddr)) {
         dev_addr->flags |= UCT_TCP_DEVICE_ADDR_FLAG_LOOPBACK;
         memset(pack_ptr, 0, sizeof(uct_iface_local_addr_ns_t));
@@ -205,6 +211,7 @@ uct_tcp_iface_is_reachable_v2(const uct_iface_h tl_iface,
     struct sockaddr_storage remote_addr;
     char remote_addr_str[UCS_SOCKADDR_STRING_LEN];
     unsigned ndev_index;
+    int allow_default_gw;
     ucs_status_t status;
 
     if (!uct_iface_is_reachable_params_valid(
@@ -263,8 +270,12 @@ uct_tcp_iface_is_reachable_v2(const uct_iface_h tl_iface,
         return 0;
     }
 
+    allow_default_gw = !!(tcp_dev_addr->flags &
+                          UCT_TCP_DEVICE_ADDR_FLAG_ALLOW_DEFAULT_GW);
+
     if (!ucs_netlink_route_exists(ndev_index,
-                                  (const struct sockaddr *)&remote_addr)) {
+                                  (const struct sockaddr *)&remote_addr,
+                                  allow_default_gw)) {
         uct_iface_fill_info_str_buf(
                     params, "no route to %s",
                     ucs_sockaddr_str((const struct sockaddr *)&remote_addr,