/
dial.go
111 lines (95 loc) · 2.9 KB
/
dial.go
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package netutil
import (
"context"
"net"
"sync"
"time"
"github.com/pkg/errors"
)
//go:generate mockery --name=Dialer --case=underscore --outpkg=netmock
type Dialer interface {
DialContext(ctx context.Context, net, addr string) (net.Conn, error)
}
var _ Dialer = &net.Dialer{}
type DialerFunc func(ctx context.Context, network, address string) (net.Conn, error)
func (f DialerFunc) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
return f(ctx, network, address)
}
// NewDNSCachingDialer returns dialer with primitive DNS caching logic
// that remembers remote address on first try, and use it in future.
func NewDNSCachingDialer(dialer Dialer, cache DNSCache) DialerFunc {
return func(ctx context.Context, network, addr string) (conn net.Conn, err error) {
resolved, ok := cache.Get(addr)
if ok {
return dialer.DialContext(ctx, network, resolved)
}
conn, err = dialer.DialContext(ctx, network, addr)
if err != nil {
return
}
remoteAddr := conn.RemoteAddr().(*net.TCPAddr)
_, port, err := net.SplitHostPort(addr)
if err != nil {
_ = conn.Close()
return nil, errors.Wrap(err, "invalid address, but successful dial - should not happen")
}
cache.Add(addr, net.JoinHostPort(remoteAddr.IP.String(), port))
return
}
}
var DefaultDNSCache = &SimpleDNSCache{}
// LookupReachable tries to resolve addr via connecting to it.
// This method has much more overhead, but get guaranteed reachable resolved addr.
// Example: host is resolved to IPv4 and IPv6, but IPv4 is not working on machine.
// LookupReachable will return IPv6 in that case.
func LookupReachable(addr string, timeout time.Duration) (string, error) {
d := net.Dialer{DualStack: true, Timeout: timeout}
conn, err := d.Dial("tcp", addr)
if err != nil {
return "", err
}
defer conn.Close()
_, port, err := net.SplitHostPort(addr)
if err != nil {
return "", err
}
remoteAddr := conn.RemoteAddr().(*net.TCPAddr)
return net.JoinHostPort(remoteAddr.IP.String(), port), nil
}
// WarmDNSCache tries connect to addr, and adds conn remote ip + addr port to cache.
func WarmDNSCache(c DNSCache, addr string) error {
var d net.Dialer
conn, err := NewDNSCachingDialer(&d, c).DialContext(context.Background(), "tcp", addr)
if err != nil {
return err
}
_ = conn.Close()
return nil
}
//go:generate mockery --name=DNSCache --case=underscore --outpkg=netmock
type DNSCache interface {
Get(addr string) (string, bool)
Add(addr, resolved string)
}
type SimpleDNSCache struct {
rw sync.RWMutex
hostToAddr map[string]string
}
func (c *SimpleDNSCache) Get(addr string) (resolved string, ok bool) {
c.rw.RLock()
if c.hostToAddr == nil {
c.rw.RUnlock()
return
}
resolved, ok = c.hostToAddr[addr]
c.rw.RUnlock()
return
}
func (c *SimpleDNSCache) Add(addr, resolved string) {
c.rw.Lock()
if c.hostToAddr == nil {
c.hostToAddr = make(map[string]string)
}
c.hostToAddr[addr] = resolved
c.rw.Unlock()
}