linux下通过netlink 获取系统路由及接口地址信息

platform: ubuntu 8.10 server

gcc version: gcc version 4.3.2

#include <linux/types.h> #include <asm/types.h> #include <inttypes.h> #include <sys/file.h> #include <sys/user.h> #include <sys/socket.h> #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <linux/if.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <stdio.h> #include <stdbool.h> #include <errno.h> typedef uint32_t u32; typedef uint16_t u16; struct nlsock { int sock; int seq; struct sockaddr_nl snl; char *name; } nl_cmd = { -1, 0, {0}, "netlink-cmd" }; static int index_oif = 0; struct nl_if_info { u32 addr; char *name; }; static int nl_socket ( struct nlsock *nl, unsigned long groups ) { int ret; struct sockaddr_nl snl; int sock; int namelen; sock = socket ( AF_NETLINK, SOCK_RAW, NETLINK_ROUTE ); if ( sock < 0 ) { fprintf ( stderr, "Can't open %s socket: %s", nl->name, strerror ( errno ) ); return -1; } ret = fcntl ( sock, F_SETFL, O_NONBLOCK ); if ( ret < 0 ) { fprintf ( stderr, "Can't set %s socket flags: %s", nl->name, strerror ( errno ) ); close ( sock ); return -1; } memset ( &snl, 0, sizeof snl ); snl.nl_family = AF_NETLINK; snl.nl_groups = groups; /* Bind the socket to the netlink structure for anything. */ ret = bind ( sock, ( struct sockaddr * ) &snl, sizeof snl ); if ( ret < 0 ) { fprintf ( stderr, "Can't bind %s socket to group 0x%x: %s", nl->name, snl.nl_groups, strerror ( errno ) ); close ( sock ); return -1; } /* multiple netlink sockets will have different nl_pid */ namelen = sizeof snl; ret = getsockname ( sock, ( struct sockaddr * ) &snl, &namelen ); if ( ret < 0 || namelen != sizeof snl ) { fprintf ( stderr, "Can't get %s socket name: %s", nl->name, strerror ( errno ) ); close ( sock ); return -1; } nl->snl = snl; nl->sock = sock; return ret; } static int nl_request ( int family, int type, struct nlsock *nl ) { int ret; struct sockaddr_nl snl; struct { struct nlmsghdr nlh; struct rtgenmsg g; } req; /* Check netlink socket. */ if ( nl->sock < 0 ) { fprintf ( stderr, "%s socket isn't active.", nl->name ); return -1; } memset ( &snl, 0, sizeof snl ); snl.nl_family = AF_NETLINK; req.nlh.nlmsg_len = sizeof req; req.nlh.nlmsg_type = type; req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST; req.nlh.nlmsg_pid = 0; req.nlh.nlmsg_seq = ++nl->seq; req.g.rtgen_family = family; ret = sendto ( nl->sock, ( void* ) &req, sizeof req, 0, ( struct sockaddr* ) &snl, sizeof snl ); if ( ret < 0 ) { fprintf ( stderr, "%s sendto failed: %s", nl->name, strerror ( errno ) ); return -1; } return 0; } /* Receive message from netlink interface and pass those information to the given function. */ static int nl_parse_info ( int ( *filter ) ( struct sockaddr_nl *, struct nlmsghdr *, void * ), struct nlsock *nl, void *arg ) { int status; int ret = 0; int error; while ( 1 ) { char buf[4096]; struct iovec iov = { buf, sizeof buf }; struct sockaddr_nl snl; struct msghdr msg = { ( void* ) &snl, sizeof snl, &iov, 1, NULL, 0, 0}; struct nlmsghdr *h; status = recvmsg ( nl->sock, &msg, 0 ); if ( status < 0 ) { if ( errno == EINTR ) continue; if ( errno == EWOULDBLOCK || errno == EAGAIN ) break; fprintf ( stderr, "%s recvmsg overrun", nl->name ); continue; } if ( snl.nl_pid != 0 ) { fprintf ( stderr, "Ignoring non kernel message from pid %u", snl.nl_pid ); continue; } if ( status == 0 ) { fprintf ( stderr, "%s EOF", nl->name ); return -1; } if ( msg.msg_namelen != sizeof snl ) { fprintf ( stderr, "%s sender address length error: length %d", nl->name, msg.msg_namelen ); return -1; } for ( h = ( struct nlmsghdr * ) buf; NLMSG_OK ( h, status ); h = NLMSG_NEXT ( h, status ) ) { /* Finish of reading. */ if ( h->nlmsg_type == NLMSG_DONE ) return ret; /* Error handling. */ if ( h->nlmsg_type == NLMSG_ERROR ) { struct nlmsgerr *err = ( struct nlmsgerr * ) NLMSG_DATA ( h ); /* If the error field is zero, then this is an ACK */ if ( err->error == 0 ) { /* return if not a multipart message, otherwise continue */ if ( ! ( h->nlmsg_flags & NLM_F_MULTI ) ) { return 0; } continue; } if ( h->nlmsg_len < NLMSG_LENGTH ( sizeof ( struct nlmsgerr ) ) ) { fprintf ( stderr, "%s error: message truncated", nl->name ); return -1; } fprintf ( stderr, "%s error: %s, type=%u, seq=%u, pid=%d", nl->name, strerror ( -err->error ), err->msg.nlmsg_type, err->msg.nlmsg_seq, err->msg.nlmsg_pid ); /* ret = -1; continue; */ return -1; } /* skip unsolicited messages originating from command socket */ if ( nl != &nl_cmd && h->nlmsg_pid == nl_cmd.snl.nl_pid ) { continue; } error = ( *filter ) ( &snl, h, arg ); if ( error < 0 ) { fprintf ( stderr, "%s filter function error\n", nl->name ); ret = error; } } /* After error care. */ if ( msg.msg_flags & MSG_TRUNC ) { fprintf ( stderr, "%s error: message truncated", nl->name ); continue; } if ( status ) { fprintf ( stderr, "%s error: data remnant size %d", nl->name, status ); return -1; } } return ret; } static void nl_parse_rtattr ( struct rtattr **tb, int max, struct rtattr *rta, int len ) { while ( RTA_OK ( rta, len ) ) { if ( rta->rta_type <= max ) tb[rta->rta_type] = rta; rta = RTA_NEXT ( rta,len ); } } static int nl_get_oif ( struct sockaddr_nl *snl, struct nlmsghdr *h, void *arg ) { int len; struct rtmsg *rtm; struct rtattr *tb [RTA_MAX + 1]; u_char flags = 0; char anyaddr[16] = {0}; int index; int table; void *dest; void *gate; rtm = NLMSG_DATA ( h ); if ( h->nlmsg_type != RTM_NEWROUTE ) return 0; if ( rtm->rtm_type != RTN_UNICAST ) return 0; table = rtm->rtm_table; len = h->nlmsg_len - NLMSG_LENGTH ( sizeof ( struct rtmsg ) ); if ( len < 0 ) return -1; memset ( tb, 0, sizeof tb ); nl_parse_rtattr ( tb, RTA_MAX, RTM_RTA ( rtm ), len ); if ( rtm->rtm_flags & RTM_F_CLONED ) return 0; if ( rtm->rtm_protocol == RTPROT_REDIRECT ) return 0; if ( rtm->rtm_protocol == RTPROT_KERNEL ) return 0; if ( rtm->rtm_src_len != 0 ) return 0; // 这里可以对所有路由进行识别 // 取得out interface index if ( tb[RTA_OIF] ) { index = * ( int * ) RTA_DATA ( tb[RTA_OIF] ); } if ( tb[RTA_DST] ) dest = RTA_DATA ( tb[RTA_DST] ); else dest = anyaddr; /* Multipath treatment is needed. */ if ( tb[RTA_GATEWAY] ) gate = RTA_DATA ( tb[RTA_GATEWAY] ); // 判断是否为默认路由 if ( dest == anyaddr && gate ) { if ( arg != NULL ) { * ( int * ) arg = index; return 0; } } return 0; } static int nl_get_if_addr ( struct sockaddr_nl *snl, struct nlmsghdr *h, void *arg ) { int len; struct ifaddrmsg *ifa; struct rtattr *tb [IFA_MAX + 1]; void *addr = NULL; void *broad = NULL; u_char flags = 0; char *label = NULL; u32 ifa_addr, ifa_local; char ifa_label[IFNAMSIZ + 1]; ifa = NLMSG_DATA ( h ); if ( ifa->ifa_family != AF_INET ) return 0; if ( h->nlmsg_type != RTM_NEWADDR && h->nlmsg_type != RTM_DELADDR ) return 0; len = h->nlmsg_len - NLMSG_LENGTH ( sizeof ( struct ifaddrmsg ) ); if ( len < 0 ) return -1; memset ( tb, 0, sizeof tb ); nl_parse_rtattr ( tb, IFA_MAX, IFA_RTA ( ifa ), len ); if (tb[IFA_ADDRESS] == NULL) tb[IFA_ADDRESS] = tb[IFA_LOCAL]; if ( tb[IFA_ADDRESS] ) ifa_addr = *(u32 *) RTA_DATA ( tb[IFA_ADDRESS] ); if ( tb[IFA_LOCAL] ) ifa_local = *(u32 *) RTA_DATA ( tb[IFA_LOCAL] ); if ( tb[IFA_LABEL] ) strncpy( ifa_label, RTA_DATA ( tb[IFA_LABEL] ), IFNAMSIZ ); // 打印所有地址信息 printf( "addr=%08x loal=%08x name=%s\n", ifa_addr, ifa_local, ifa_label ); return 0; } int main() { int ret; char if_name[PAGE_SIZE]; char *p; struct nl_if_info if_info = { -1, "eth0" }; ret = nl_socket ( &nl_cmd, 0 ); if ( ret < 0 ) { return ret; } ret = nl_request ( AF_INET, RTM_GETROUTE, &nl_cmd ); if ( ret < 0 ) { return ret; } ret = nl_parse_info ( nl_get_oif, &nl_cmd, &index_oif ); if ( ret < 0 ) return ret; printf ( "oif=%08x \n", index_oif ); if ( index_oif > 0 ) { p = if_indextoname ( index_oif, if_name ); if ( p ) { printf ( "interface=%s\n", p ); } } ret = nl_request ( AF_INET, RTM_GETADDR, &nl_cmd ); if ( ret < 0 ) return ret; ret = nl_parse_info ( nl_get_if_addr, &nl_cmd, &if_info ); if ( ret < 0 ) return ret; return 0; }

参考:

1> RFC3549 - Linux Netlink as an IP Services Protocol

2> Zebra Source code

3> netlink(7) - Linux man page