netlink: improved event handling

src/netlink.cpp

@@ -68,11 +68,7 @@ void Netlink::connect() {
 }
 
 void Netlink::subscribe() const {
-  struct iovec iov[3];
-
-  prepare_iovec(iov);
-
-  if (writev(nl_socket, iov, 3) == -1) {
+  if (nl_subscribe(nl_socket) == -1) {
     util::debug("failed to send PROC_CN_MCAST_LISTEN!");
   } else {
     util::debug("sent PROC_CN_MCAST_LISTEN to kernel");

src/netlink_c.c

@@ -3,14 +3,17 @@
 #include <linux/cn_proc.h>
 #include <linux/connector.h>
 #include <linux/netlink.h>
+#include <sys/uio.h>
 #include <unistd.h>
 
 /*
   It was necessary to separate the code using "<linux/cn_proc.h>" because one of its line can only be compiled in a
   C compiler...
 */
 
-void prepare_iovec(struct iovec iov[3]) {
+int nl_subscribe(int nl_socket) {
+  struct iovec iov[3];
+
   char buff[NLMSG_LENGTH(0)];
   struct cn_msg cnmsg;
   enum proc_cn_mcast_op mcast_op = PROC_CN_MCAST_LISTEN;
@@ -43,6 +46,8 @@ void prepare_iovec(struct iovec iov[3]) {
 
   iov[2].iov_base = &mcast_op;
   iov[2].iov_len = sizeof(mcast_op);
+
+  return writev(nl_socket, iov, 3);
 }
 
 struct fg_cn_msg parse_cn_msg(struct cn_msg* msg) {

src/netlink_c.h

@@ -33,7 +33,7 @@ struct fg_cn_msg {
   enum fg_proc_cn_event event;
 };
 
-void prepare_iovec(struct iovec iov[3]);
+int nl_subscribe(int nl_socket);
 
 struct fg_cn_msg parse_cn_msg(struct cn_msg* msg);