/* $Id: getroute.c,v 1.4 2013/02/06 10:50:04 nanard Exp $ */ /* MiniUPnP project * http://miniupnp.free.fr/ or http://miniupnp.tuxfamily.org/ * (c) 2006-2013 Thomas Bernard * This software is subject to the conditions detailed * in the LICENCE file provided within the distribution */ #include <stdio.h> #include <string.h> #include <unistd.h> #include <errno.h> #include <syslog.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> /*#include <linux/in_route.h>*/ #include <linux/netlink.h> #include <linux/rtnetlink.h> #include <libnfnetlink/libnfnetlink.h> #include "../getroute.h" #include "../upnputils.h" int get_src_for_route_to(const struct sockaddr * dst, void * src, size_t * src_len, int * index) { int fd = -1; struct nlmsghdr *h; int status; struct { struct nlmsghdr n; struct rtmsg r; char buf[1024]; } req; struct sockaddr_nl nladdr; struct iovec iov = { .iov_base = (void*) &req.n, }; struct msghdr msg = { .msg_name = &nladdr, .msg_namelen = sizeof(nladdr), .msg_iov = &iov, .msg_iovlen = 1, }; const struct sockaddr_in * dst4; const struct sockaddr_in6 * dst6; memset(&req, 0, sizeof(req)); req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); req.n.nlmsg_flags = NLM_F_REQUEST; req.n.nlmsg_type = RTM_GETROUTE; req.r.rtm_family = dst->sa_family; req.r.rtm_table = 0; req.r.rtm_protocol = 0; req.r.rtm_scope = 0; req.r.rtm_type = 0; req.r.rtm_src_len = 0; req.r.rtm_dst_len = 0; req.r.rtm_tos = 0; { char dst_str[128]; sockaddr_to_string(dst, dst_str, sizeof(dst_str)); syslog(LOG_DEBUG, "get_src_for_route_to (%s)", dst_str); } /* add address */ if(dst->sa_family == AF_INET) { dst4 = (const struct sockaddr_in *)dst; nfnl_addattr_l(&req.n, sizeof(req), RTA_DST, &dst4->sin_addr, 4); req.r.rtm_dst_len = 32; } else { dst6 = (const struct sockaddr_in6 *)dst; nfnl_addattr_l(&req.n, sizeof(req), RTA_DST, &dst6->sin6_addr, 16); req.r.rtm_dst_len = 128; } fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); if (fd < 0) { syslog(LOG_ERR, "socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE) : %m"); return -1; } memset(&nladdr, 0, sizeof(nladdr)); nladdr.nl_family = AF_NETLINK; req.n.nlmsg_seq = 1; iov.iov_len = req.n.nlmsg_len; status = sendmsg(fd, &msg, 0); if (status < 0) { syslog(LOG_ERR, "sendmsg(rtnetlink) : %m"); goto error; } memset(&req, 0, sizeof(req)); for(;;) { iov.iov_len = sizeof(req); status = recvmsg(fd, &msg, 0); if(status < 0) { if (errno == EINTR || errno == EAGAIN) continue; syslog(LOG_ERR, "recvmsg(rtnetlink) %m"); goto error; } if(status == 0) { syslog(LOG_ERR, "recvmsg(rtnetlink) EOF"); goto error; } for (h = (struct nlmsghdr*)&req.n; status >= (int)sizeof(*h); ) { int len = h->nlmsg_len; int l = len - sizeof(*h); if (l<0 || len>status) { if (msg.msg_flags & MSG_TRUNC) { syslog(LOG_ERR, "Truncated message"); } syslog(LOG_ERR, "malformed message: len=%d", len); goto error; } if(nladdr.nl_pid != 0 || h->nlmsg_seq != 1/*seq*/) { syslog(LOG_ERR, "wrong seq = %d\n", h->nlmsg_seq); /* Don't forget to skip that message. */ status -= NLMSG_ALIGN(len); h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len)); continue; } if(h->nlmsg_type == NLMSG_ERROR) { struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(h); syslog(LOG_ERR, "NLMSG_ERROR %d : %s", err->error, strerror(-err->error)); goto error; } if(h->nlmsg_type == RTM_NEWROUTE) { struct rtattr * rta; int len = h->nlmsg_len; len -= NLMSG_LENGTH(sizeof(struct rtmsg)); for(rta = RTM_RTA(NLMSG_DATA((h))); RTA_OK(rta, len); rta = RTA_NEXT(rta,len)) { unsigned char * data = RTA_DATA(rta); if(rta->rta_type == RTA_PREFSRC) { if(src_len && src) { if(*src_len < RTA_PAYLOAD(rta)) { syslog(LOG_WARNING, "cannot copy src: %u<%lu", (unsigned)*src_len, RTA_PAYLOAD(rta)); goto error; } *src_len = RTA_PAYLOAD(rta); memcpy(src, data, RTA_PAYLOAD(rta)); } } else if(rta->rta_type == RTA_OIF) { if(index) memcpy(index, data, sizeof(int)); } } close(fd); return 0; } status -= NLMSG_ALIGN(len); h = (struct nlmsghdr*)((char*)h + NLMSG_ALIGN(len)); } } syslog(LOG_WARNING, "get_src_for_route_to() : src not found"); error: if(fd >= 0) close(fd); return -1; }