Retry failed netlink operations

The stack sends three requests to the kernel using
the netlink socket. If the kernel is e.g. busy at this point,
netlink will respond with a EBUSY error value.

The current code does not handle these errors gracefully, but instead
silently ignores them. This can lead to vsomeip stack being stalled,
and not starting certain services, e.g. service discovery.

This patch helps fix these issues by sending a retry of the messages
that fail.

1 files changed, 33 insertions, 4 deletions

diff --git a/implementation/endpoints/src/netlink_connector.cpp b/implementation/endpoints/src/netlink_connector.cpp
index ce82e9f..ebd432d 100644
--- a/implementation/endpoints/src/netlink_connector.cpp
+++ b/implementation/endpoints/src/netlink_connector.cpp
@@ -17,6 +17,12 @@
 
 namespace vsomeip_v3 {
 
+namespace {
+    const std::uint32_t ifa_request_sequence = 1;
+    const std::uint32_t ifi_request_sequence = 2;
+    const std::uint32_t rt_request_sequence = 3;
+}
+
 void netlink_connector::register_net_if_changes_handler(const net_if_changed_handler_t& _handler) {
     handler_ = _handler;
 }
@@ -181,9 +187,32 @@ void netlink_connector::receive_cbk(boost::system::error_code const &_error,
                 }
                 case NLMSG_ERROR: {
                     struct nlmsgerr *errmsg = (nlmsgerr *)NLMSG_DATA(nlh);
+                    if (errmsg->error == 0) {
+                        // Ack from netlink
+                        break;
+                    }
+
                     VSOMEIP_ERROR << "netlink_connector::receive_cbk received "
-                        "error message: " << std::dec << nlh->nlmsg_type
+                        "error message: " << strerror(errmsg->error)
+                        << " type " << std::dec << errmsg->msg.nlmsg_type
                         << " seq " << errmsg->msg.nlmsg_seq;
+
+                    std::string request_type{};
+                    if (errmsg->msg.nlmsg_type == RTM_GETADDR && errmsg->msg.nlmsg_seq == ifa_request_sequence) {
+                        request_type = "address request";
+                        send_ifa_request();
+                    } else if (errmsg->msg.nlmsg_type == RTM_GETLINK && errmsg->msg.nlmsg_seq == ifi_request_sequence) {
+                        request_type = "link request";
+                        send_ifi_request();
+                    } else if (errmsg->msg.nlmsg_type == RTM_GETROUTE && errmsg->msg.nlmsg_seq == rt_request_sequence) {
+                        request_type = "route request";
+                        send_rt_request();
+                    }
+
+                    if (!request_type.empty()) {
+                        VSOMEIP_INFO << "Retrying netlink " << request_type;
+                    }
+
                     break;
                 }
                 case NLMSG_DONE:
@@ -251,7 +280,7 @@ void netlink_connector::send_ifa_request() {
     get_address_msg.nlhdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
     get_address_msg.nlhdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT;
     get_address_msg.nlhdr.nlmsg_type = RTM_GETADDR;
-    get_address_msg.nlhdr.nlmsg_seq = 1;
+    get_address_msg.nlhdr.nlmsg_seq = ifa_request_sequence;
     if (address_.is_v4()) {
         get_address_msg.addrmsg.ifa_family = AF_INET;
     } else {
@@ -280,7 +309,7 @@ void netlink_connector::send_ifi_request() {
     get_link_msg.nlhdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT;
     get_link_msg.nlhdr.nlmsg_type = RTM_GETLINK;
     get_link_msg.infomsg.ifi_family = AF_UNSPEC;
-    get_link_msg.nlhdr.nlmsg_seq = 2;
+    get_link_msg.nlhdr.nlmsg_seq = ifi_request_sequence;
 
     {
         std::lock_guard<std::mutex> its_lock(socket_mutex_);
@@ -307,7 +336,7 @@ void netlink_connector::send_rt_request() {
     get_route_msg.nlhdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg));
     get_route_msg.nlhdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
     get_route_msg.nlhdr.nlmsg_type = RTM_GETROUTE;
-    get_route_msg.nlhdr.nlmsg_seq = 3;
+    get_route_msg.nlhdr.nlmsg_seq = rt_request_sequence;
     if (multicast_address_.is_v6()) {
         get_route_msg.routemsg.rtgen_family = AF_INET6;
     } else {