Initial netlink support

We now are able to know when a device is going down, handling that event
is further work.

Author: sargon

Makefile

@@ -1,4 +1,4 @@
-OBJ=main.o ddhcp.o netsock.o packet.o dhcp.o dhcp_packet.o dhcp_options.o tools.o block.o control.o hook.o logger.o statistics.o epoll.o
+OBJ=main.o ddhcp.o netsock.o packet.o dhcp.o dhcp_packet.o dhcp_options.o tools.o block.o control.o hook.o logger.o statistics.o epoll.o netlink.o
 OBJCTL=ddhcpctl.o netsock.o packet.o dhcp.o dhcp_packet.o dhcp_options.o tools.o block.o hook.o logger.o
 HDRS=$(wildcard *.h)
 
@@ -26,7 +26,8 @@ CFLAGS+= \
     -Wswitch-default \
     -Wswitch-enum \
     -Wunreachable-code \
-    -Winit-self
+    -Winit-self \
+    `pkg-config --cflags libnl-3.0`
 
 CXXFLAGS+= \
     ${CFLAGS} \
@@ -36,7 +37,8 @@ CXXFLAGS+= \
 
 LFLAGS+= \
     -flto \
-    -lm
+    -lm \
+    `pkg-config --libs libnl-3.0`
 
 ifeq ($(DEBUG),1)
 CFLAGS+= \

main.c

@@ -21,6 +21,7 @@
 #include "epoll.h"
 #include "hook.h"
 #include "logger.h"
+#include "netlink.h"
 #include "netsock.h"
 #include "packet.h"
 #include "statistics.h"
@@ -469,11 +470,13 @@ int main(int argc, char** argv) {
   config.sockets[SKT_MCAST] = epoll_data_new(interface, netsock_multicast_init, hdl_ddhcp_block, NULL);
   config.sockets[SKT_SERVER] = epoll_data_new(interface, netsock_server_init, hdl_ddhcp_dhcp, NULL);
   config.sockets[SKT_CONTROL] = epoll_data_new(config.control_path, netsock_control_init, hdl_ctrl_new, NULL);
+  ddhcp_epoll_data* netlink = epoll_data_new(NULL, netlink_init, netlink_in, netlink_close);
 
   // Trigger socket initializing and register to EPOLL
   epoll_add_fd(config.epoll_fd, config.sockets[SKT_MCAST], EPOLLIN | EPOLLET,&config);
   epoll_add_fd(config.epoll_fd, config.sockets[SKT_SERVER], EPOLLIN | EPOLLET,&config);
   epoll_add_fd(config.epoll_fd, config.sockets[SKT_CONTROL], EPOLLIN | EPOLLET,&config);
+  epoll_add_fd(config.epoll_fd, netlink, EPOLLIN | EPOLLET,&config);
 
   if (config.disable_dhcp == 0) {
     config.sockets[SKT_DHCP] = epoll_data_new(interface_client, netsock_dhcp_init, hdl_dhcp, NULL);
@@ -577,6 +580,7 @@ int main(int argc, char** argv) {
   //close(config.mcast_socket);
   //close(config.client_socket);
   //close(config.control_socket);
+  epoll_data_call(netlink,epollhup,(&config));
 
   remove(config.control_path);
 

netlink.c

@@ -0,0 +1,77 @@
+#include <net/if.h>
+#include <netlink/msg.h>
+#include <netlink/netlink.h>
+#include <netlink/socket.h>
+
+#include "epoll.h"
+#include "logger.h"
+#include "tools.h"
+#include "types.h"
+
+static int callback(struct nl_msg *msg, void* vcfg) {
+  ddhcp_config *config = (ddhcp_config*) vcfg;
+  struct nlmsghdr* hdr = nlmsg_hdr(msg);
+
+  DEBUG("netlink_callback(...): callback triggered\n");
+
+  if (hdr->nlmsg_type == RTM_NEWLINK) {
+    struct ifinfomsg* data = NLMSG_DATA(hdr);
+    if (DDHCP_SKT_SERVER(config)->interface_id == data->ifi_index) {
+      DEBUG("netlink_callback(...): action on server interface\n");
+    }
+    if (data->ifi_flags & IFF_UP) {
+      DEBUG("netlink_callback(...): iface(%i) up\n",data->ifi_index);
+    } else {
+      DEBUG("netlink_callback(...): iface(%i) down\n",data->ifi_index);
+    }
+  } 
+
+  if (hdr->nlmsg_type == RTM_DELLINK) {
+    struct ifinfomsg* data = NLMSG_DATA(hdr);
+    DEBUG("netlink_callback(...): iface(%i) deleted\n",data->ifi_index);
+  }
+
+  return 0;
+}
+
+ATTR_NONNULL_ALL int netlink_in(epoll_data_t data,ddhcp_config* config) {
+  UNUSED(config);
+  ddhcp_epoll_data* ptr = (ddhcp_epoll_data*) data.ptr;
+  return nl_recvmsgs_default((struct nl_sock*) ptr->data);
+}
+
+ATTR_NONNULL_ALL int netlink_init(epoll_data_t data,ddhcp_config* config) {
+  ddhcp_epoll_data* ptr = (ddhcp_epoll_data*) data.ptr;
+  DEBUG("netlink_init(config)\n");
+  struct nl_sock *sock;
+
+  sock = nl_socket_alloc();
+
+  if (sock == NULL) {
+    FATAL("netlink_init(...): Unable to open netlink socket\n");
+    return -1;
+  }
+
+  nl_socket_disable_seq_check(sock);
+  nl_socket_set_nonblocking(sock);
+  nl_socket_modify_cb(sock,NL_CB_VALID,NL_CB_CUSTOM,callback,(void*) config);
+
+  if (nl_connect(sock, NETLINK_ROUTE) < 0) {
+    FATAL("netlink_init(...): Unable to connect to netlink route module");
+    return -1;
+  } else {
+    ptr->fd = nl_socket_get_fd(sock);
+    ptr->data = (void*) sock;
+  }
+
+  nl_socket_add_memberships(sock, RTNLGRP_LINK, 0);
+
+  return 0;
+}
+
+ATTR_NONNULL_ALL int netlink_close(epoll_data_t data, ddhcp_config* config) {
+  UNUSED(config);
+  ddhcp_epoll_data* ptr = (ddhcp_epoll_data*) data.ptr;
+  nl_socket_free((struct nl_sock*) ptr->data);
+  return 0;
+}

netlink.h

@@ -0,0 +1,10 @@
+#ifndef _NETLINK_H
+#define _NETLINK_H
+
+#include "types.h"
+#include "epoll.h"
+
+ATTR_NONNULL_ALL int netlink_init(epoll_data_t data,ddhcp_config* config);
+ATTR_NONNULL_ALL int netlink_in(epoll_data_t data,ddhcp_config* config);
+ATTR_NONNULL_ALL int netlink_close(epoll_data_t,ddhcp_config* config);
+#endif