Netlink的简单例子

采用Netlink进行内核与用户空间交互数据

参考：netlink学习笔记之NETLINK_INET_DIAG获取TCP连接状态(netstat) – 浮生笔记

比如获取连接状态

#if 0
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <asm/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/inet_diag.h>
#include <netinet/tcp.h>int main(int argc, char **argv)
{int fd;struct sockaddr_nl src_addr, dest_addr;struct{struct nlmsghdr nlh;struct inet_diag_req r;} req;struct inet_diag_msg *pkg;struct msghdr msg;char buf[8192];char src_ip[40];char dest_ip[40];struct iovec iov;if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG)) < 0)return -1;int ret;ret = fcntl(fd, F_SETFL, O_NONBLOCK);if (ret < 0) {fprintf(stderr, "Can't set socket flags");close(fd);return -1;}//src addrmemset(&src_addr, 0, sizeof(struct sockaddr_nl));src_addr.nl_family = AF_NETLINK;src_addr.nl_pid = getpid();src_addr.nl_groups = 0;if (bind(fd, (struct sockaddr *)&src_addr, sizeof(struct sockaddr_nl)) < 0) {fprintf(stderr, "bind socket error %s\n", strerror(errno));}memset(&req, 0, sizeof(req));req.nlh.nlmsg_len = sizeof(req);req.nlh.nlmsg_type = TCPDIAG_GETSOCK;req.nlh.nlmsg_flags = NLM_F_MATCH | NLM_F_REQUEST | NLM_F_ROOT;// req.nlh.nlmsg_flags = NLM_F_REQUEST ;req.nlh.nlmsg_pid = 0;memset(&req.r, 0, sizeof(req.r));req.r.idiag_family = AF_INET;req.r.idiag_states = ((1 << TCP_CLOSING + 1) - 1); //states to dump//send msg to kerneliov.iov_base = &req;iov.iov_len = sizeof(req);//dest addrmemset(&dest_addr, 0, sizeof(struct sockaddr_nl));dest_addr.nl_family = AF_NETLINK;dest_addr.nl_pid = 0;dest_addr.nl_groups = 0;msg.msg_name = (void *)&dest_addr;msg.msg_namelen = sizeof(dest_addr);msg.msg_iov = &iov;msg.msg_iovlen = 1;if (sendmsg(fd, &msg, 0) < 0) {printf("%s\n", strerror(errno));return -1;}//recv msg from kerneliov.iov_base = buf;iov.iov_len = sizeof(buf);while (1) {//printf("while1\n");int status;struct nlmsghdr *h;msg = (struct msghdr){(void *)&dest_addr, sizeof(struct sockaddr_nl),&iov, 1, NULL, 0, 0};//length of recv datastatus = recvmsg(fd, &msg, 0);//status = recv(fd, buf, sizeof(buf), 0);printf("status = %d\n", status);if (status < 0) {if (errno == EINTR) {continue;}printf("errno = %d\n", errno);continue;}if (status == 0) {close(fd);printf("EOF\n");return 0;}h = (struct nlmsghdr *)buf;while (NLMSG_OK(h, status)) {//printf("while2\n");printf("nlmsg_type = %d\n",h->nlmsg_type );if (h->nlmsg_type == NLMSG_DONE) {close(fd);printf("NLMSG_DONE\n");return 0;}if (h->nlmsg_type == NLMSG_ERROR) {struct nlmsgerr *err;err = (struct nlmsgerr*)NLMSG_DATA(h);fprintf(stderr, "%d Error %d:%s\n", __LINE__, -(err->error), strerror(-(err->error)));close(fd);printf("NLMSG_ERROR\n");return 0;}pkg = (struct inet_diag_msg *)NLMSG_DATA(h);memset(src_ip, 0, sizeof(src_ip));memset(dest_ip, 0, sizeof(dest_ip));inet_ntop(pkg->idiag_family, pkg->id.idiag_src, src_ip, sizeof(src_ip));inet_ntop(pkg->idiag_family, pkg->id.idiag_dst, dest_ip, sizeof(dest_ip));printf("%-8s %4d %40s:%-6hu %40s:%-6hu\n", pkg->idiag_family == AF_INET ? "AF_INET" : "AF_INET6", pkg->idiag_state, src_ip, ntohs(pkg->id.idiag_sport), dest_ip, ntohs(pkg->id.idiag_dport));// get_tcp_state(pkg->idiag_state);h = NLMSG_NEXT(h, status);//printf("status = %d\n\n", status);}//while}//whileclose(fd);return 0;
}#else
/*** @file NET_LINK_NET_STATE.c* @author dennisthink (https://www.dennisthink.com/)* @brief NETLINK方式获取 网络连接状态* @version 0.1* @date 2020-11-21* * @copyright Copyright (c) 2020* */#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <asm/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/inet_diag.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>/*** @brief 创建NetLinkDiag的socket* * @return int > 0 创建成功*             - 1 创建失败*/
int createNetLinkDiagSocket()
{int fd = 0;if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG)) < 0){return -1;}    else{return fd;}
}/*** @brief 设置socket为非阻塞模式* * @param fd 被设置的socket描述符* @return int >= 0  -- 成功*             -1 -- 失败*/
int setSocketOpt(int fd)
{int ret = 0;ret = fcntl(fd, F_SETFL, O_NONBLOCK);if (ret < 0){fprintf(stderr, "Can't set socket flags");close(fd);return -1;}else{return ret;}
}/*** @brief 绑定socket到NetLink的地址* * @param fd 待绑定的socket* @return int 0  --- 成功*             -1 --- 失败*/
int bindSocketToNetLink(int fd)
{struct sockaddr_nl src_addr;{//src addrmemset(&src_addr, 0, sizeof(struct sockaddr_nl));src_addr.nl_family = AF_NETLINK;src_addr.nl_pid = getpid();src_addr.nl_groups = 0;}if (bind(fd, (struct sockaddr *)&src_addr, sizeof(struct sockaddr_nl)) >=0 ){return 0;}else{return -1;}
}/*** @brief 发送消息到内核* * @param fd netlink的socket* @return int 0  -- 成功*             -1 -- 失败*/
int sendMsgToNetLink(int fd)
{//4.1 初始化目标地址struct sockaddr_nl dest_addr;{memset(&dest_addr, 0, sizeof(struct sockaddr_nl));dest_addr.nl_family = AF_NETLINK;dest_addr.nl_pid = 0;dest_addr.nl_groups = 0;}//4.2 初始化请求的数据struct{struct nlmsghdr nlh;struct inet_diag_req r;} req;{memset(&req, 0, sizeof(req));req.nlh.nlmsg_len = sizeof(req);req.nlh.nlmsg_type = TCPDIAG_GETSOCK;req.nlh.nlmsg_flags = NLM_F_MATCH | NLM_F_REQUEST | NLM_F_ROOT;// req.nlh.nlmsg_flags = NLM_F_REQUEST ;req.nlh.nlmsg_pid = 0;memset(&req.r, 0, sizeof(req.r));req.r.idiag_family = AF_INET;req.r.idiag_states = ((1 << TCP_CLOSING + 1) - 1); //states to dump}//4.3 将请求数据绑定到消息上//4.3.1 将req数据绑定到iov上//注意:此处要定义一个数组,保存足够的buff，要不会出现 errno=105的错误struct iovec iov[2];char buff[4096]={0};{//send msg to kerneliov[0].iov_base = &req;iov[0].iov_len = sizeof(req);iov[1].iov_base = buff;iov[1].iov_len = sizeof(buff);}struct msghdr msgForSend;//4.3.2 将目标地址和请求数据绑定到msg上{msgForSend.msg_name = (void *)&dest_addr;msgForSend.msg_namelen = sizeof(dest_addr);msgForSend.msg_iov = iov;msgForSend.msg_iovlen = 2;}//4.4 发送消息if (sendmsg(fd, &msgForSend, 0) < 0){return -1;}return 0;
}/*** @brief 解析TCP的状态* * @param nState tcp状态*/
void parseTcpState(const int nState)
{switch(nState){case TCP_ESTABLISHED:{printf("ESTABLISHED");}break;case TCP_SYN_SENT:{printf("SYN_SENT");}break;case TCP_SYN_RECV:{printf("SYN_RECV");}break;case TCP_FIN_WAIT1:{printf("FIN_WAIT1");}break;case TCP_FIN_WAIT2:{printf("FIN_WAIT2");}break;case TCP_TIME_WAIT:{printf("TIME_WAIT");}break;case TCP_CLOSE:{printf("CLOSE");}break;case TCP_CLOSE_WAIT:{printf("CLOSE_WAIT");}break;case TCP_LAST_ACK:{printf("LAST_ACK");}break;case TCP_CLOSING:{printf("CLOSING");}break;case TCP_LISTEN:{printf("LISTEN");}break;default:{printf("DEFAULT");}break;}
}/*** @brief 解析收到的数据* * @param buff 数据起始地址* @param status 数据的长度* @return int 默认返回0*/
int parseRecvMsg(char *buff,int status)
{struct nlmsghdr * h = (struct nlmsghdr *)buff;while (NLMSG_OK(h, status)){if (h->nlmsg_type == NLMSG_DONE){printf("NLMSG_DONE\n");return 0;}if (h->nlmsg_type == NLMSG_ERROR){struct nlmsgerr *err;err = (struct nlmsgerr *)NLMSG_DATA(h);fprintf(stderr, "%d Error %d:%s\n", __LINE__, -(err->error), strerror(-(err->error)));return 0;}struct inet_diag_msg *pkg = (struct inet_diag_msg *)NLMSG_DATA(h);char src_ip[40];char dest_ip[40];memset(src_ip, 0, sizeof(src_ip));memset(dest_ip, 0, sizeof(dest_ip));inet_ntop(pkg->idiag_family, pkg->id.idiag_src, src_ip, sizeof(src_ip));inet_ntop(pkg->idiag_family, pkg->id.idiag_dst, dest_ip, sizeof(dest_ip));printf("%-8s %40s:%-6hu %40s:%-6hu", pkg->idiag_family == AF_INET ? "AF_INET" : "AF_INET6", src_ip, ntohs(pkg->id.idiag_sport), dest_ip, ntohs(pkg->id.idiag_dport));parseTcpState(pkg->idiag_state);printf("\n");h = NLMSG_NEXT(h, status);} //whilereturn 0;
}
/*** @brief 从netlink接收消息* * @param fd netlink套接字* @return int 默认返回0*/
int recvMsgFromNetLink(int fd)
{char buf[8192]={0};//recv msg from kernelstruct iovec iov;iov.iov_base = buf;iov.iov_len = sizeof(buf);struct sockaddr_nl destAddrForRecv;{memset(&destAddrForRecv, 0, sizeof(struct sockaddr_nl));destAddrForRecv.nl_family = AF_NETLINK;destAddrForRecv.nl_pid = 0;destAddrForRecv.nl_groups = 0;}struct msghdr msgForRecv;while (1){msgForRecv.msg_name = (void *)(&destAddrForRecv);msgForRecv.msg_namelen = sizeof(destAddrForRecv);msgForRecv.msg_iov = &iov;msgForRecv.msg_iovlen  = 1;//length of recv dataint status = recvmsg(fd, &msgForRecv, 0);if (status == 0){return 0;}if(status > 0){parseRecvMsg(buf,status);return 0;}usleep(1000);}//whilereturn 0;
}int main(int argc, char **argv)
{//创建socketint fd = createNetLinkDiagSocket();if(fd > 0){printf("Create Socket Succeed\n");}else{printf("Create Socket Failed  ErrNo:%d  ErrMsg:%s\n",errno,strerror(errno));return -1;}//2. 设置socket选项if(setSocketOpt(fd) >= 0){printf("Set socketOpt succeed \n");}else{printf("Set sockOpt faild  ErrNo:%d  ErrMsg:%s\n",errno,strerror(errno));return -1;}//3. 绑定socketif(bindSocketToNetLink(fd) >= 0){printf("bind Socket To NetLink Succeed\n");}else{printf("bind Socket To NetLink faild  ErrNo:%d  ErrMsg:%s\n",errno,strerror(errno));return -1;}//4. 发送消息到内核if(sendMsgToNetLink(fd) >= 0){printf("sendMsgToNetLink Succeed \n");}else{printf("sendMsgToNetLink Failed ErrNo:%d  ErrMsg:%s\n",errno,strerror(errno));return -1;}if(recvMsgFromNetLink(fd)>=0){printf("recvMsgFromNetLink Succeed\n");}else{printf("recvMsgFromNetLink Failed ErrNo:%d  ErrMsg:%s\n",errno,strerror(errno));}close(fd);return 0;
}#endif

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