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C++

// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2012-2017 OpenVPN Inc.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License Version 3
// as published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program in the COPYING file.
// If not, see <http://www.gnu.org/licenses/>.
// Get IPv4 gateway info on Mac OS X.
#ifndef OPENVPN_TUN_MAC_GWV4_H
#define OPENVPN_TUN_MAC_GWV4_H
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/route.h>
#include <net/if.h>
#include <net/if_dl.h>
#include <cstring>
#include <string>
#include <sstream>
#include <algorithm> // for std::max
#include <cstdint> // for std::uint32_t
#include <memory>
#include <openvpn/common/exception.hpp>
#include <openvpn/common/hexstr.hpp>
#include <openvpn/common/scoped_fd.hpp>
#include <openvpn/common/socktypes.hpp>
#include <openvpn/common/string.hpp>
#include <openvpn/addr/ip.hpp>
#include <openvpn/addr/addrpair.hpp>
#include <openvpn/addr/macaddr.hpp>
namespace openvpn {
class MacGatewayInfoV4
{
struct rtmsg {
struct rt_msghdr m_rtm;
char m_space[512];
};
# define OPENVPN_ROUNDUP(a) \
((a) > 0 ? (1 + (((a) - 1) | (sizeof(std::uint32_t) - 1))) : sizeof(std::uint32_t))
# define OPENVPN_NEXTADDR(w, u) \
if (rtm_addrs & (w)) { \
l = OPENVPN_ROUNDUP(u.sa_len); \
std::memmove(cp, &(u), l); \
cp += l; \
}
# define OPENVPN_ADVANCE(x, n) \
(x += OPENVPN_ROUNDUP((n)->sa_len))
public:
OPENVPN_EXCEPTION(route_gateway_error);
enum {
ADDR_DEFINED = (1<<0), /* set if gateway.addr defined */
NETMASK_DEFINED = (1<<1), /* set if gateway.netmask defined */
HWADDR_DEFINED = (1<<2), /* set if hwaddr is defined */
IFACE_DEFINED = (1<<3), /* set if iface is defined */
};
MacGatewayInfoV4()
: flags_(0)
{
struct rtmsg m_rtmsg;
ScopedFD sockfd;
int seq, l, pid, rtm_addrs, i;
struct sockaddr so_dst, so_mask;
char *cp = m_rtmsg.m_space;
struct sockaddr *gate = nullptr, *ifp = nullptr, *sa;
struct rt_msghdr *rtm_aux;
/* setup data to send to routing socket */
pid = ::getpid();
seq = 0;
rtm_addrs = RTA_DST | RTA_NETMASK | RTA_IFP;
std::memset(&m_rtmsg, 0, sizeof(m_rtmsg));
std::memset(&so_dst, 0, sizeof(so_dst));
std::memset(&so_mask, 0, sizeof(so_mask));
std::memset(&m_rtmsg.m_rtm, 0, sizeof(struct rt_msghdr));
m_rtmsg.m_rtm.rtm_type = RTM_GET;
m_rtmsg.m_rtm.rtm_flags = RTF_UP | RTF_GATEWAY;
m_rtmsg.m_rtm.rtm_version = RTM_VERSION;
m_rtmsg.m_rtm.rtm_seq = ++seq;
m_rtmsg.m_rtm.rtm_addrs = rtm_addrs;
so_dst.sa_family = AF_INET;
so_dst.sa_len = sizeof(struct sockaddr_in);
so_mask.sa_family = AF_INET;
so_mask.sa_len = sizeof(struct sockaddr_in);
OPENVPN_NEXTADDR(RTA_DST, so_dst);
OPENVPN_NEXTADDR(RTA_NETMASK, so_mask);
m_rtmsg.m_rtm.rtm_msglen = l = cp - (char *)&m_rtmsg;
/* transact with routing socket */
sockfd.reset(socket(PF_ROUTE, SOCK_RAW, 0));
if (!sockfd.defined())
throw route_gateway_error("GDG: socket #1 failed");
if (::write(sockfd(), (char *)&m_rtmsg, l) < 0)
throw route_gateway_error("GDG: problem writing to routing socket");
do {
l = ::read(sockfd(), (char *)&m_rtmsg, sizeof(m_rtmsg));
} while (l > 0 && (m_rtmsg.m_rtm.rtm_seq != seq || m_rtmsg.m_rtm.rtm_pid != pid));
sockfd.close();
/* extract return data from routing socket */
rtm_aux = &m_rtmsg.m_rtm;
cp = ((char *)(rtm_aux + 1));
if (rtm_aux->rtm_addrs)
{
for (i = 1; i; i <<= 1)
{
if (i & rtm_aux->rtm_addrs)
{
sa = (struct sockaddr *)cp;
if (i == RTA_GATEWAY )
gate = sa;
else if (i == RTA_IFP)
ifp = sa;
OPENVPN_ADVANCE(cp, sa);
}
}
}
else
return;
/* get gateway addr and interface name */
if (gate != nullptr )
{
/* get default gateway addr */
gateway_.addr.reset_ipv4_from_uint32(ntohl(((struct sockaddr_in *)gate)->sin_addr.s_addr));
if (!gateway_.addr.unspecified())
flags_ |= ADDR_DEFINED;
if (ifp)
{
/* get interface name */
const struct sockaddr_dl *adl = (struct sockaddr_dl *) ifp;
const size_t len = adl->sdl_nlen;
if (len && len < sizeof(iface_))
{
std::memcpy (iface_, adl->sdl_data, len);
iface_[len] = '\0';
flags_ |= IFACE_DEFINED;
}
}
}
/* get netmask of interface that owns default gateway */
if (flags_ & IFACE_DEFINED) {
struct ifreq ifr;
sockfd.reset(socket(AF_INET, SOCK_DGRAM, 0));
if (!sockfd.defined())
throw route_gateway_error("GDG: socket #2 failed");
std::memset(&ifr, 0, sizeof(ifr));
ifr.ifr_addr.sa_family = AF_INET;
string::strncpynt(ifr.ifr_name, iface_, IFNAMSIZ);
if (::ioctl(sockfd(), SIOCGIFNETMASK, (char *)&ifr) < 0)
throw route_gateway_error("GDG: ioctl #1 failed");
sockfd.close();
gateway_.netmask.reset_ipv4_from_uint32(ntohl(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr.s_addr));
flags_ |= NETMASK_DEFINED;
}
/* try to read MAC addr associated with interface that owns default gateway */
if (flags_ & IFACE_DEFINED)
{
struct ifconf ifc;
struct ifreq *ifr;
const int bufsize = 4096;
std::unique_ptr<char[]> buffer(new char[bufsize]);
std::memset(buffer.get(), 0, bufsize);
sockfd.reset(socket(AF_INET, SOCK_DGRAM, 0));
if (!sockfd.defined())
throw route_gateway_error("GDG: socket #3 failed");
ifc.ifc_len = bufsize;
ifc.ifc_buf = buffer.get();
if (::ioctl(sockfd(), SIOCGIFCONF, (char *)&ifc) < 0)
throw route_gateway_error("GDG: ioctl #2 failed");
sockfd.close();
for (cp = buffer.get(); cp <= buffer.get() + ifc.ifc_len - sizeof(struct ifreq); )
{
ifr = (struct ifreq *)cp;
const size_t len = sizeof(ifr->ifr_name) + std::max(sizeof(ifr->ifr_addr), size_t(ifr->ifr_addr.sa_len));
if (!ifr->ifr_addr.sa_family)
break;
if (!::strncmp(ifr->ifr_name, iface_, IFNAMSIZ))
{
if (ifr->ifr_addr.sa_family == AF_LINK)
{
struct sockaddr_dl *sdl = (struct sockaddr_dl *)&ifr->ifr_addr;
hwaddr_.reset((const unsigned char *)LLADDR(sdl));
flags_ |= HWADDR_DEFINED;
}
}
cp += len;
}
}
}
# undef OPENVPN_ROUNDUP
# undef OPENVPN_NEXTADDR
# undef OPENVPN_ADVANCE
std::string info() const
{
std::ostringstream os;
os << "GATEWAY";
if (flags_ & ADDR_DEFINED)
{
os << " ADDR=" << gateway_.addr;
if (flags_ & NETMASK_DEFINED)
{
os << '/' << gateway_.netmask;
}
}
if (flags_ & IFACE_DEFINED)
os << " IFACE=" << iface_;
if (flags_ & HWADDR_DEFINED)
os << " HWADDR=" << hwaddr_;
return os.str();
}
unsigned int flags() const { return flags_; }
const IP::Addr& gateway_addr() const { return gateway_.addr; }
std::string gateway_addr_str() const { return gateway_addr().to_string(); }
const IP::Addr& gateway_netmask() const { return gateway_.netmask; }
std::string gateway_netmask_str() const { return gateway_netmask().to_string(); }
std::string iface() const { return iface_; }
const MACAddr& hwaddr() const { return hwaddr_; }
bool iface_addr_defined() const
{
return (flags_ & (ADDR_DEFINED|IFACE_DEFINED)) == (ADDR_DEFINED|IFACE_DEFINED);
}
bool hwaddr_defined() const
{
return flags_ & HWADDR_DEFINED;
}
private:
unsigned int flags_;
IP::AddrMaskPair gateway_;
char iface_[16];
MACAddr hwaddr_;
};
}
#endif