跪求使用netlink查询路由中返回信息处理的代码，写了一半了，帮忙补下吧！

souldump

#include <netpacket/packet.h>
#include <net/ethernet.h>
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/ioctl.h>
#include<net/if.h>
#include<netinet/ip.h>
#include<err.h>
#include<netdb.h>
#include<fcntl.h>
#include<linux/netlink.h>
#include<linux/rtnetlink.h>
#include<net/route.h>

struct req {
          struct nlmsghdr nlmsg;
          struct rtmsg rtm;
          char buf[512];
};

int print_route(struct rtentry *rt);
int main(void)
{


        int fd;
        int n;
        char *c;
        char buff[BUFSIZ];
        char str[22];
        struct req req;
       
          struct nlmsghdr nlmsg, *nlp;
          struct rtmsg rtm;
        struct sockaddr so;
        struct sockaddr_nl nl;
        struct in_addr addr;

        fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
        if (fd < 0) {
                perror("open error");
                exit (1);
        }
        nl.nl_family = AF_NETLINK;
        nl.nl_pad = 0;
        nl.nl_pid = getpid();
        nl.nl_groups = 0;

        n = bind(fd, (struct sockaddr*)&nl, sizeof(nl));
        if (n < 0) {
                perror(" bind  error");
                exit (1);
        }

        memset(&nlmsg, 0, sizeof(struct nlmsghdr));
        req.nlmsg.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
        req.nlmsg.nlmsg_type = RTM_GETROUTE;
        req.nlmsg.nlmsg_flags = NLM_F_ROOT|NLM_F_REQUEST;
//        req.nlmsg.nlmsg_pid = nl.pid;  

        memset(&rtm, 0, sizeof(struct rtmsg));
        req.rtm.rtm_family = AF_NETLINK;
       
        /** we need change here **/
        req.rtm.rtm_dst_len = 4;
        req.rtm.rtm_src_len = 4;

        req.rtm.rtm_table = RT_TABLE_MAIN;
        req.rtm.rtm_protocol = RTPROT_BOOT;/* Route installed during boot                */
        req.rtm.rtm_scope = RT_SCOPE_LINK; /** located on directly LAN **/
        req.rtm.rtm_type = RTN_UNICAST;        /** Gateway or direct route **/

        n = send(fd, &req, sizeof(req), 0);
        if (n < 0)
        {
                perror("send error!");
                exit (-1);
        }
        else
                printf("%d bytes send!\n",n);

        n = recv(fd, buff, BUFSIZ, 0);
        if (n < 0)
                perror("received failed!");
        printf("%d bytes received!\n", n);
/**********************在这里开始加就好了**********************/

               
        }
}

这段代码烦了好几天了，有人说返回 nlmsghdr + route entry. route entry 又由几个
rtattr结构组成。可我还是没法理解。总是弄不出来。
哪个大哥帮添加一下吧，比如打印目的地址和网关。不愿意写，把详细的数据结构介绍下
也好，多谢了！

souldump

自己的事情自己做！

不好意思，上面的代码有点乱。这是完整的代码。

2. #include<stdio.h>
3. #include<stdlib.h>
4. #include<string.h>
5. #include<unistd.h>
6. #include<sys/socket.h>
7. #include<netinet/in.h>
8. #include<sys/types.h>
9. #include<linux/netlink.h>
10. #include<linux/rtnetlink.h>
12. struct req {
13.           struct nlmsghdr nlmsg;
14.           struct rtmsg rtm;
15. };
17. struct rtattr* get_gw_attr(struct nlmsghdr *nlmsghdr);
18. int print_route(struct rtattr *rtp);
19. int main(void)
20. {
21.         int fd;
22.         int n;
23.         char *c;
24.         char buff[BUFSIZ];
25.         char str[22];
26.         struct req req;
27.         struct rtattr *rtp;
28.           struct nlmsghdr nlmsg, *nlp;
29.           struct rtmsg rtm;
30.         struct sockaddr so;
31.         struct sockaddr_nl nl;
32.         struct in_addr addr;
34.         fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
35.         if (fd < 0) {
36.                 perror("open error");
37.                 exit (1);
38.         }
39.         nl.nl_family = AF_NETLINK;
40.         nl.nl_pad = 0;
41.         nl.nl_pid = getpid();
42.         nl.nl_groups = 0;
44.         n = bind(fd, (struct sockaddr*)&nl, sizeof(nl));
45.         if (n < 0) {
46.                 perror(" bind  error");
47.                 exit (1);
48.         }
50.         memset(&nlmsg, 0, sizeof(struct nlmsghdr));
51.         req.nlmsg.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
52.         req.nlmsg.nlmsg_type = RTM_GETROUTE;
54.         /** In kernel header comments NLM_F_ROOT "specify tree root", but On somebooks
55.           * said this means return the entire table not just one entry **/
56.         req.nlmsg.nlmsg_flags = NLM_F_ROOT|NLM_F_REQUEST;
57. //        req.nlmsg.nlmsg_pid = nl.pid;  /** this is not required! **/
59.         memset(&rtm, 0, sizeof(struct rtmsg));
60.         req.rtm.rtm_family = AF_NETLINK;
61.        
62.         /** we need change here **/
63.         req.rtm.rtm_dst_len = 4;
64.         req.rtm.rtm_src_len = 4;
66.         req.rtm.rtm_table = RT_TABLE_MAIN;
67.         req.rtm.rtm_protocol = RTPROT_BOOT;/** Route installed during boot **/
68.         req.rtm.rtm_scope = RT_SCOPE_LINK; /** located on directly LAN **/
69.         req.rtm.rtm_type = RTN_UNICAST;        /** Gateway or direct route **/
71.         n = send(fd, &req, sizeof(req), 0);
72.         if (n < 0)
73.         {
74.                 perror("send error!");
75.                 exit (-1);
76.         }
77.         else
78.                 printf("%d bytes send!\n",n);
80.         n = recv(fd, buff, BUFSIZ, 0);
81.         if (n < 0)
82.                 perror("received failed!");
84.         printf("%d bytes received!\n", n);
85.         for (nlp = (struct nlmsghdr*)buff; \
86.                 (nlp->nlmsg_type != NLMSG_DONE)&& NLMSG_OK(nlp, n); nlp = NLMSG_NEXT(nlp, n)) {
87.                 rtp = get_gw_attr(nlp);
88.                 if (rtp) {
89.                         print_route(rtp);
90.                         return;
91.                 }
92.         }
93. }
94. struct rtattr* get_gw_attr(struct nlmsghdr *nlmsghdr)
95. {
96.         struct rtattr *rta;
97.         int len;
98.         int gw;
99.         char str[16];
101.         len = nlmsghdr->nlmsg_len - NLMSG_LENGTH(sizeof(struct rtmsg));
103.         /** NLMSG_DATA(nlmsghdr) return the rtmsg pointer following, and RTM_RTA return
104.                 the rtattr pointer following the rtmsg.        **/
105.         rta = RTM_RTA(NLMSG_DATA(nlmsghdr));
106.         while (RTA_OK(rta, len)) {
107.                 if (rta->rta_type >= RTA_MAX)
108.                         break;
109.                 /** We check if the address is INADDR_ANY.I don't know whethher this is needed **/
110.                 if(rta->rta_type == RTA_GATEWAY && *(int *)RTA_DATA(rta) != INADDR_ANY)
111.                                 return rta;
112.                 rta = RTA_NEXT(rta, len);
113.         }
114.         return NULL;
115. };
116. int print_route(struct rtattr *rtp)
117. {
118.         char str[16];
119.         char *c;
120.         char buff[16];
121.         c = inet_ntop (AF_INET, RTA_DATA(rtp), buff, INET_ADDRSTRLEN);
122.         if (!c) {
123.                 perror("inet_ntop failed !");
124.                 exit (1);
125.         }
126.         printf("The gateway IP address is %s\n",c);
127. }

复制代码

参考：
1. http://people.redhat.com/nhorman/papers/netlink.pdf
2. RFC3549：http://rfc.net/rfc3549.html

详细的过程我不想解释，因为上面的两个参考资料足够了。而我也正开始学习整理一份完整的NETLINK实现和编程的文章。
希望早日能出炉拿出来和大家分享。


说实话，我不知道是我问的方式不对，还是论坛里的高手不想回答，抑或是没有人知道。

realtang

楼主是个挺不错的guy，说真的，用linux内核接口NETLINK的人确实比较少。你的这篇文章也很有参考价值。
我为你加精，为你加油。
希望你能为GNU的事业再努力。
这里的很多老鸟相继的都退隐江湖了，好在现在的情况是新秀层出不穷。

souldump

谢谢版主，这几天正忙毕业设计呢，想早点弄完，下半年就没事做了。那就有时间研究内核了。

liwang820716

楼主，我爱死你了！！！

Augustin

可以在linuxjournal中搜一下netlink,有两篇文章专门讲这个,也写的很好.