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netlink-examples
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| // Netlink 是内核与用户空间进程通信的一种机制，采用与 UDP socket 非常类似的编程风格。（ | |
| // 与 UDP 类似，Netlink 通信也有服务器端和客户端。例如，Linux 内核作为服务器端，已经运行在那里。我们则编写 Netlink 客户端，给内核发消息，并获得我们想要的信息。 | |
| /* | |
| * Display all IPv4 addresses | |
| */ | |
| #include <stdio.h> //printf, perror | |
| #include <string.h> //memset, strlen | |
| #include <stdlib.h> //exit | |
| #include <unistd.h> //close | |
| #include <sys/socket.h> //msghdr | |
| #include <arpa/inet.h> //inet_ntop | |
| #include <linux/netlink.h> //sockaddr_nl | |
| #include <linux/rtnetlink.h> //rtgenmsg,ifinfomsg | |
| #define BUFSIZE 8192 | |
| struct nl_req_s { | |
| struct nlmsghdr hdr; | |
| struct rtgenmsg gen; | |
| }; | |
| void die(char *s) | |
| { | |
| perror(s); | |
| exit(1); | |
| } | |
| void rtnl_print_addr(struct nlmsghdr * h) | |
| { | |
| struct ifaddrmsg * addr; | |
| struct rtattr * attr; | |
| int len; | |
| addr = NLMSG_DATA(h); | |
| len = RTM_PAYLOAD(h); | |
| /* loop over all attributes for the NEWLINK message */ | |
| for (attr = IFLA_RTA(addr); RTA_OK(attr, len); attr = RTA_NEXT(attr, len)) | |
| { | |
| switch (attr->rta_type) | |
| { | |
| case IFA_LABEL: | |
| printf("Interface : %s\n", (char *)RTA_DATA(attr)); | |
| break; | |
| case IFA_LOCAL: | |
| { | |
| int ip = *(int*)RTA_DATA(attr); | |
| unsigned char bytes[4]; | |
| bytes[0] = ip & 0xFF; | |
| bytes[1] = (ip >> 8) & 0xFF; | |
| bytes[2] = (ip >> 16) & 0xFF; | |
| bytes[3] = (ip >> 24) & 0xFF; | |
| printf("IP Address : %d.%d.%d.%d\n", bytes[0], bytes[1], bytes[2], bytes[3]); | |
| break; | |
| } | |
| default: | |
| break; | |
| } | |
| } | |
| } | |
| int main(void) | |
| { | |
| struct sockaddr_nl kernel; | |
| int s, end=0, len; | |
| struct msghdr msg; | |
| struct nl_req_s req; | |
| struct iovec io; | |
| char buf[BUFSIZE]; | |
| //build kernel netlink address | |
| memset(&kernel, 0, sizeof(kernel)); | |
| kernel.nl_family = AF_NETLINK; | |
| kernel.nl_groups = 0; | |
| //create a Netlink socket | |
| if ((s=socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0) | |
| { | |
| die("socket"); | |
| } | |
| //build netlink message | |
| memset(&req, 0, sizeof(req)); | |
| req.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg)); | |
| req.hdr.nlmsg_type = RTM_GETADDR; | |
| req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP; | |
| req.hdr.nlmsg_seq = 1; | |
| req.hdr.nlmsg_pid = getpid(); | |
| req.gen.rtgen_family = AF_INET; | |
| memset(&io, 0, sizeof(io)); | |
| io.iov_base = &req; | |
| io.iov_len = req.hdr.nlmsg_len; | |
| memset(&msg, 0, sizeof(msg)); | |
| msg.msg_iov = &io; | |
| msg.msg_iovlen = 1; | |
| msg.msg_name = &kernel; | |
| msg.msg_namelen = sizeof(kernel); | |
| //send the message | |
| if (sendmsg(s, &msg, 0) < 0) | |
| { | |
| die("sendmsg"); | |
| } | |
| //parse reply | |
| while (!end) | |
| { | |
| memset(buf, 0, BUFSIZE); | |
| msg.msg_iov->iov_base = buf; | |
| msg.msg_iov->iov_len = BUFSIZE; | |
| if ((len=recvmsg(s, &msg, 0)) < 0) | |
| { | |
| die("recvmsg"); | |
| } | |
| for (struct nlmsghdr * msg_ptr = (struct nlmsghdr *)buf; | |
| NLMSG_OK(msg_ptr, len); msg_ptr = NLMSG_NEXT(msg_ptr, len)) | |
| { | |
| switch (msg_ptr->nlmsg_type) | |
| { | |
| case NLMSG_DONE: | |
| end++; | |
| break; | |
| case RTM_NEWADDR: | |
| rtnl_print_addr(msg_ptr); | |
| break; | |
| default: | |
| printf("Ignored msg: type=%d, len=%d\n", msg_ptr->nlmsg_type, msg_ptr->nlmsg_len); | |
| break; | |
| } | |
| } | |
| } | |
| close(s); | |
| return 0; | |
| } | |
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| /* | |
| * Display all network interface names | |
| */ | |
| #include <stdio.h> //printf, perror | |
| #include <string.h> //memset, strlen | |
| #include <stdlib.h> //exit | |
| #include <unistd.h> //close | |
| #include <sys/socket.h> //msghdr | |
| #include <arpa/inet.h> //inet_ntop | |
| #include <linux/netlink.h> //sockaddr_nl | |
| #include <linux/rtnetlink.h> //rtgenmsg,ifinfomsg | |
| #define BUFSIZE 8192 | |
| struct nl_req_s { | |
| struct nlmsghdr hdr; | |
| struct rtgenmsg gen; | |
| }; | |
| void die(char *s) | |
| { | |
| perror(s); | |
| exit(1); | |
| } | |
| void rtnl_print_link(struct nlmsghdr * h) | |
| { | |
| struct ifinfomsg * iface; | |
| struct rtattr * attr; | |
| int len; | |
| iface = NLMSG_DATA(h); | |
| len = RTM_PAYLOAD(h); | |
| /* loop over all attributes for the NEWLINK message */ | |
| for (attr = IFLA_RTA(iface); RTA_OK(attr, len); attr = RTA_NEXT(attr, len)) | |
| { | |
| switch (attr->rta_type) | |
| { | |
| case IFLA_IFNAME: | |
| printf("Interface %d : %s\n", iface->ifi_index, (char *)RTA_DATA(attr)); | |
| break; | |
| default: | |
| break; | |
| } | |
| } | |
| } | |
| int main(void) | |
| { | |
| struct sockaddr_nl kernel; | |
| int s, end=0, len; | |
| struct msghdr msg; | |
| struct nl_req_s req; | |
| struct iovec io; | |
| char buf[BUFSIZE]; | |
| //build kernel netlink address | |
| memset(&kernel, 0, sizeof(kernel)); | |
| kernel.nl_family = AF_NETLINK; | |
| kernel.nl_groups = 0; | |
| //create a Netlink socket | |
| if ((s=socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0) | |
| { | |
| die("socket"); | |
| } | |
| //build netlink message | |
| memset(&req, 0, sizeof(req)); | |
| req.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg)); | |
| req.hdr.nlmsg_type = RTM_GETLINK; | |
| req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP; | |
| req.hdr.nlmsg_seq = 1; | |
| req.hdr.nlmsg_pid = getpid(); | |
| req.gen.rtgen_family = AF_INET; | |
| memset(&io, 0, sizeof(io)); | |
| io.iov_base = &req; | |
| io.iov_len = req.hdr.nlmsg_len; | |
| memset(&msg, 0, sizeof(msg)); | |
| msg.msg_iov = &io; | |
| msg.msg_iovlen = 1; | |
| msg.msg_name = &kernel; | |
| msg.msg_namelen = sizeof(kernel); | |
| //send the message | |
| if (sendmsg(s, &msg, 0) < 0) | |
| { | |
| die("sendmsg"); | |
| } | |
| //parse reply | |
| while (!end) | |
| { | |
| memset(buf, 0, BUFSIZE); | |
| msg.msg_iov->iov_base = buf; | |
| msg.msg_iov->iov_len = BUFSIZE; | |
| if ((len=recvmsg(s, &msg, 0)) < 0) | |
| { | |
| die("recvmsg"); | |
| } | |
| for (struct nlmsghdr * msg_ptr = (struct nlmsghdr *)buf; | |
| NLMSG_OK(msg_ptr, len); msg_ptr = NLMSG_NEXT(msg_ptr, len)) | |
| { | |
| switch (msg_ptr->nlmsg_type) | |
| { | |
| case NLMSG_DONE: | |
| end++; | |
| break; | |
| case RTM_NEWLINK: | |
| rtnl_print_link(msg_ptr); | |
| break; | |
| default: | |
| printf("Ignored msg: type=%d, len=%d\n", msg_ptr->nlmsg_type, msg_ptr->nlmsg_len); | |
| break; | |
| } | |
| } | |
| } | |
| close(s); | |
| return 0; | |
| } |
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