/
UDPConn.go
98 lines (85 loc) · 2.76 KB
/
UDPConn.go
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/*
* Copyright (c) 2018, Psiphon Inc.
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package psiphon
import (
"context"
"math/rand"
"net"
"strconv"
"syscall"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/errors"
)
// NewUDPConn resolves addr and configures a new UDP conn. The UDP socket is
// created using options in DialConfig, including DeviceBinder. The returned
// UDPAddr uses DialConfig options IPv6Synthesizer and ResolvedIPCallback.
//
// The UDP conn is not dialed; it is intended for use with WriteTo using the
// returned UDPAddr, not Write.
//
// The returned conn is not a Closer; the caller is expected to wrap this conn
// with another higher-level conn that provides that interface.
func NewUDPConn(
ctx context.Context, addr string, config *DialConfig) (net.PacketConn, *net.UDPAddr, error) {
host, strPort, err := net.SplitHostPort(addr)
if err != nil {
return nil, nil, errors.Trace(err)
}
port, err := strconv.Atoi(strPort)
if err != nil {
return nil, nil, errors.Trace(err)
}
if port <= 0 || port >= 65536 {
return nil, nil, errors.Tracef("invalid destination port: %d", port)
}
ipAddrs, err := LookupIP(ctx, host, config)
if err != nil {
return nil, nil, errors.Trace(err)
}
if len(ipAddrs) < 1 {
return nil, nil, errors.TraceNew("no IP address")
}
ipAddr := ipAddrs[rand.Intn(len(ipAddrs))]
if config.IPv6Synthesizer != nil {
if ipAddr.To4() != nil {
synthesizedIPAddress := config.IPv6Synthesizer.IPv6Synthesize(ipAddr.String())
if synthesizedIPAddress != "" {
synthesizedAddr := net.ParseIP(synthesizedIPAddress)
if synthesizedAddr != nil {
ipAddr = synthesizedAddr
}
}
}
}
var domain int
if ipAddr != nil && ipAddr.To4() != nil {
domain = syscall.AF_INET
} else if ipAddr != nil && ipAddr.To16() != nil {
domain = syscall.AF_INET6
} else {
return nil, nil, errors.Tracef("invalid IP address: %s", ipAddr.String())
}
conn, err := newUDPConn(domain, config)
if err != nil {
return nil, nil, errors.Trace(err)
}
if config.ResolvedIPCallback != nil {
config.ResolvedIPCallback(ipAddr.String())
}
return conn, &net.UDPAddr{IP: ipAddr, Port: port}, nil
}