netlink示例程序：监听网络状态变化

PROG=netlink
OBJS=netlink.o
CFLAGS =
LDFLAGS=-static
NDK_HOME ?=/opt/android-ndk-r9d

ifeq ($(ARM),1)
SYSROOT=$(NDK_HOME)/platforms/android-19/arch-arm/
CC=$(NDK_HOME)/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gcc --sysroot=$(SYSROOT)
PROG=netlink.arm
OBJS:=$(OBJS:.o=.arm.o)
else
ifeq ($(ndk),1)
SYSROOT=$(NDK_HOME)/platforms/android-19/arch-x86/
CC=$(NDK_HOME)/toolchains/x86-4.8/prebuilt/linux-x86_64/bin/i686-linux-android-gcc --sysroot=$(SYSROOT)
endif

ifeq ($(DEBUG),1)
CFLAGS += -g -ggdb
endif

#CFLAGS += -m32
#LDFLAGS += -m32

endif

all: $(PROG)

netlink: $(OBJS)
$(CC) $(LDFLAGS) -o $@ $^

netlink.arm: $(OBJS)
$(CC) $(LDFLAGS) -o $@ $^

%.o:%.c
$(CC) $(CFLAGS) -c -o $@ $<

%.arm.o:%.c
$(CC) $(CFLAGS) -c -o $@ $<

clean:
rm -rf *.o netlink netlink.arm

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/if.h>

#include <netinet/in.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
//#include <net/if.h>
#include <arpa/inet.h>

#include <signal.h>

FILE* fp=NULL;
int running = 1;

void nl_log(const char* fmt, ...)
{
va_list ap;

va_start(ap, fmt);
if(fp != NULL){
if (vfprintf(fp, fmt, ap) < 0){
perror("fprintf");
}
fflush(fp);
}
vprintf(fmt, ap);
va_end(ap);
}

void parseBinaryNetlinkMessage(struct nlmsghdr *nh) {
int len = nh->nlmsg_len - sizeof(*nh);
struct ifinfomsg *ifi;

if (sizeof(*ifi) > (size_t) len) {
nl_log("Got a short RTM_NEWLINK message\n");
return;
}

ifi = (struct ifinfomsg *)NLMSG_DATA(nh);
if ((ifi->ifi_flags & IFF_LOOPBACK) != 0) {
return;
}

struct rtattr *rta = (struct rtattr *)
((char *) ifi + NLMSG_ALIGN(sizeof(*ifi)));
len = NLMSG_PAYLOAD(nh, sizeof(*ifi));

while(RTA_OK(rta, len)) {
switch(rta->rta_type) {
case IFLA_IFNAME:
{
char ifname[IFNAMSIZ];
char *action;
snprintf(ifname, sizeof(ifname), "%s",
(char *) RTA_DATA(rta));
//action = (ifi->ifi_flags & IFF_LOWER_UP) ? "up" : "down";
action = (ifi->ifi_flags & IFF_RUNNING) ? "up" : "down";
nl_log("%s link %s\n", ifname, action);
}
}

rta = RTA_NEXT(rta, len);
}
}

void parseNetlinkAddrMsg(struct nlmsghdr *nlh, int new)
{
struct ifaddrmsg *ifa = (struct ifaddrmsg *) NLMSG_DATA(nlh);
struct rtattr *rth = IFA_RTA(ifa);
int rtl = IFA_PAYLOAD(nlh);

while (rtl && RTA_OK(rth, rtl)) {
if (rth->rta_type == IFA_LOCAL) {
uint32_t ipaddr = htonl(*((uint32_t *)RTA_DATA(rth)));
char name[IFNAMSIZ];
if_indextoname(ifa->ifa_index, name);
nl_log("%s %s address %d.%d.%d.%d\n",
name, (new != 0)?"add":"del",
(ipaddr >> 24) & 0xff,
(ipaddr >> 16) & 0xff,
(ipaddr >> 8) & 0xff,
ipaddr & 0xff);
}
rth = RTA_NEXT(rth, rtl);
}
}

void signal_handle(int signo)
{
nl_log("got signal:%d\n", signo);
if(fp != NULL){
fclose(fp);
}
exit(0);
}

int main(int argc, char* argv[])
{
struct sockaddr_nl addr;
int sock, len;
char buffer[4096];
struct nlmsghdr *nlh;
char* fname = "netlink.log";

if (argc > 1 && strcmp(argv[1],"-f")==0){
fp = fopen(fname, "w");
if (fp == NULL){
perror("fopen");
return 1;
}
printf("netlink message will also write to %s. \n", fname);
}

signal(SIGINT, signal_handle);
if ((sock = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) == -1) {
perror("couldn't open NETLINK_ROUTE socket");
return 1;
}

memset(&addr, 0, sizeof(addr));
addr.nl_family = AF_NETLINK;
addr.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR;

if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
perror("couldn't bind");
return 1;
}

while (running && (len = recv(sock, buffer, 4096, 0)) > 0) {
nlh = (struct nlmsghdr *)buffer;
while ((NLMSG_OK(nlh, len)) && (nlh->nlmsg_type != NLMSG_DONE)) {
if (nlh->nlmsg_type == RTM_NEWADDR) {
parseNetlinkAddrMsg(nlh, 1);
}else if(nlh->nlmsg_type == RTM_DELADDR){
parseNetlinkAddrMsg(nlh, 0);
}else if (nlh->nlmsg_type == RTM_NEWLINK){
parseBinaryNetlinkMessage(nlh);
}
nlh = NLMSG_NEXT(nlh, len);
}
}
close(sock);
if(fp != NULL){
fclose(fp);
}
return 0;
}