UCS/SYS/NETLINK: Iteratively receive netlink messages until 'done' is set

src/ucs/sys/netlink.c

@@ -44,6 +44,11 @@ KHASH_INIT(ucs_netlink_rt_cache, khint32_t, ucs_netlink_rt_rules_t, 1,
            kh_int_hash_func, kh_int_hash_equal);
 static khash_t(ucs_netlink_rt_cache) ucs_netlink_routing_table_cache;
 
+static inline int ucs_netlink_is_msg_done(const struct nlmsghdr *nlh)
+{
+    return (nlh->nlmsg_type == NLMSG_DONE);
+}
+
 static ucs_status_t ucs_netlink_socket_init(int *fd_p, int protocol)
 {
     struct sockaddr_nl sa = {.nl_family = AF_NETLINK};
@@ -78,7 +83,7 @@ ucs_netlink_parse_msg(const void *msg, size_t msg_len,
     const struct nlmsghdr *nlh = (const struct nlmsghdr *)msg;
 
     while ((status == UCS_INPROGRESS) && NLMSG_OK(nlh, msg_len) &&
-           (nlh->nlmsg_type != NLMSG_DONE)) {
+           !ucs_netlink_is_msg_done(nlh)) {
         if (nlh->nlmsg_type == NLMSG_ERROR) {
             struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(nlh);
             ucs_error("received error response from netlink err=%d: %s\n",
@@ -100,9 +105,10 @@ ucs_netlink_send_request(int protocol, unsigned short nlmsg_type,
                          ucs_netlink_parse_cb_t parse_cb, void *arg)
 {
     struct nlmsghdr nlh = {0};
-    char *recv_msg      = NULL;
-    size_t recv_msg_len = 0;
     int netlink_fd      = -1;
+    size_t recv_msg_len;
+    char *recv_msg;
+    int msg_done;
     ucs_status_t status;
     struct iovec iov[2];
     size_t bytes_sent;
@@ -131,33 +137,38 @@ ucs_netlink_send_request(int protocol, unsigned short nlmsg_type,
     }
 
     /* get message size */
-    status = ucs_socket_recv_nb(netlink_fd, NULL, MSG_PEEK | MSG_TRUNC,
-                                &recv_msg_len);
-    if (status != UCS_OK) {
-        ucs_error("failed to get netlink message size %d (%s)",
-                  status, ucs_status_string(status));
-        goto out;
-    }
+    do {
+        recv_msg_len = 0;
+        status = ucs_socket_recv_nb(netlink_fd, NULL, MSG_PEEK | MSG_TRUNC,
+                                    &recv_msg_len);
+        if (status != UCS_OK) {
+            ucs_error("failed to get netlink message size %d (%s)",
+                    status, ucs_status_string(status));
+            goto out;
+        }
 
-    recv_msg = ucs_malloc(recv_msg_len, "netlink recv message");
-    if (recv_msg == NULL) {
-        ucs_error("failed to allocate a buffer for netlink receive message of"
-                  " size %zu", recv_msg_len);
-        goto out;
-    }
+        recv_msg = ucs_malloc(recv_msg_len, "netlink recv message");
+        if (recv_msg == NULL) {
+            ucs_error("failed to allocate a buffer for netlink receive message"
+                      " of size %zu", recv_msg_len);
+            goto out;
+        }
 
-    status = ucs_socket_recv(netlink_fd, recv_msg, recv_msg_len);
-    if (status != UCS_OK) {
-        ucs_error("failed to receive netlink message on fd=%d: %s",
-                  netlink_fd, ucs_status_string(status));
-        goto out;
-    }
+        status = ucs_socket_recv(netlink_fd, recv_msg, recv_msg_len);
+        if (status != UCS_OK) {
+            ucs_error("failed to receive netlink message on fd=%d: %s",
+                    netlink_fd, ucs_status_string(status));
+            ucs_free(recv_msg);
+            goto out;
+        }
 
-    status = ucs_netlink_parse_msg(recv_msg, recv_msg_len, parse_cb, arg);
+        status   = ucs_netlink_parse_msg(recv_msg, recv_msg_len, parse_cb, arg);
+        msg_done = ucs_netlink_is_msg_done((const struct nlmsghdr *)recv_msg);
+        ucs_free(recv_msg);
+    } while ((nlmsg_flags & NLM_F_DUMP) && !msg_done);
 
 out:
     ucs_close_fd(&netlink_fd);
-    ucs_free(recv_msg);
     return status;
 }
 
@@ -262,8 +273,8 @@ int ucs_netlink_route_exists(int if_index, const struct sockaddr *sa_remote)
     ucs_netlink_route_info_t info;
 
     UCS_INIT_ONCE(&init_once) {
+        rtm.rtm_table  = RT_TABLE_UNSPEC; /* fetch all the tables */
         rtm.rtm_family = AF_INET;
-        rtm.rtm_table  = RT_TABLE_MAIN;
         ucs_netlink_send_request(NETLINK_ROUTE, RTM_GETROUTE, NLM_F_DUMP, &rtm,
                                  sizeof(rtm), ucs_netlink_parse_rt_entry_cb,
                                  NULL);