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// 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- OpenVPN Inc.
//
// SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//
// Find default gateways on Linux using ip route command
#ifndef OPENVPN_NETCONF_LINUX_GW_H
#define OPENVPN_NETCONF_LINUX_GW_H
#include <string>
#include <limits>
#include <openvpn/common/exception.hpp>
#include <openvpn/common/number.hpp>
#include <openvpn/common/split.hpp>
#include <openvpn/common/splitlines.hpp>
#include <openvpn/common/process.hpp>
#include <openvpn/addr/route.hpp>
namespace openvpn {
class LinuxGW
{
public:
OPENVPN_EXCEPTION(linux_gw_error);
LinuxGW(const std::string &ip_route_show_txt, const bool ignore_errors)
{
int best_metric = std::numeric_limits<int>::max();
SplitLines sl(ip_route_show_txt);
while (sl())
{
const std::string &line = sl.line_ref();
try
{
// parse an output line generated by "ip [-6] route show"
const std::vector<std::string> v = Split::by_space<std::vector<std::string>, NullLex, SpaceMatch, Split::NullLimit>(line);
// blank line?
if (v.empty())
continue;
// only interested in default routes
if (v[0] != "default")
continue;
// parse out route information
enum RouteInfo
{
INITIAL,
VIA,
DEV,
METRIC,
};
std::string d;
IP::Addr a;
int m = std::numeric_limits<int>::max();
RouteInfo ri = INITIAL;
for (const auto &term : v)
{
switch (ri)
{
case INITIAL:
if (term == "via")
ri = VIA;
else if (term == "dev")
ri = DEV;
else if (term == "metric")
ri = METRIC;
else
ri = INITIAL;
break;
case VIA:
a = IP::Addr(term, "via");
ri = INITIAL;
break;
case DEV:
d = validate_dev(term);
ri = INITIAL;
break;
case METRIC:
m = parse_number_throw<int>(term, "bad metric");
ri = INITIAL;
break;
}
}
// best metric?
if (m < best_metric || best_metric == std::numeric_limits<int>::max())
{
best_metric = m;
dev_ = std::move(d);
addr_ = a;
}
}
catch (const std::exception &e)
{
if (!ignore_errors)
OPENVPN_THROW(linux_gw_error, "error parsing line: " << line << " : " << e.what());
}
}
}
static std::string ip_route_show(const bool ipv6)
{
RedirectPipe::InOut pipe;
Argv argv;
argv.emplace_back("/sbin/ip");
if (ipv6)
argv.emplace_back("-6");
argv.emplace_back("route");
argv.emplace_back("show");
const int status = system_cmd(argv[0], argv, nullptr, pipe, 0, nullptr);
if (status != 0)
OPENVPN_THROW(linux_gw_error, "command returned error status " << status << " : " << argv.to_string());
return pipe.out;
}
const std::string &dev() const
{
return dev_;
}
const IP::Addr &addr() const
{
return addr_;
}
bool defined() const
{
return !dev_.empty() && addr_.defined();
}
std::string to_string() const
{
return dev_ + '/' + addr_.to_string();
}
private:
std::string validate_dev(const std::string &dev)
{
if (dev.empty())
OPENVPN_THROW_EXCEPTION("dev is empty");
return dev;
}
std::string dev_;
IP::Addr addr_;
};
struct LinuxGW46
{
LinuxGW46(const bool ignore_errors)
: v4(LinuxGW::ip_route_show(false), ignore_errors),
v6(LinuxGW::ip_route_show(true), ignore_errors)
{
}
std::string to_string() const
{
std::string ret = "[";
if (v4.defined())
{
ret += "4:";
ret += v4.to_string();
}
if (v6.defined())
{
if (v4.defined())
ret += ' ';
ret += "6:";
ret += v6.to_string();
}
ret += "]";
return ret;
}
std::string dev() const
{
if (v4.defined())
return v4.dev();
else if (v6.defined())
return v6.dev();
else
throw LinuxGW::linux_gw_error("cannot determine gateway interface");
}
LinuxGW v4;
LinuxGW v6;
};
} // namespace openvpn
#endif
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