From eb0b17bea13c13bc9dae1ed4512eb8bbfa73ca37 Mon Sep 17 00:00:00 2001
From: nadoo <287492+nadoo@users.noreply.github.com>
Date: Fri, 24 Aug 2018 18:45:57 +0800
Subject: [PATCH] strategy: add experimental dh: `destination hashing` mode

---
 strategy/dh.go       | 31 +++++++++++++++++++++++++++++++
 strategy/ha.go       | 10 ++++++++++
 strategy/lha.go      | 10 ++++++++++
 strategy/strategy.go |  3 +++
 4 files changed, 54 insertions(+)
 create mode 100644 strategy/dh.go

diff --git a/strategy/dh.go b/strategy/dh.go
new file mode 100644
index 0000000..47e2b93
--- /dev/null
+++ b/strategy/dh.go
@@ -0,0 +1,31 @@
+package strategy
+
+import (
+	"hash/fnv"
+	"net"
+
+	"github.com/nadoo/glider/proxy"
+)
+
+// destination hashing dialer
+type dhDialer struct{ *rrDialer }
+
+// newDHDialer .
+func newDHDialer(dialers []*proxy.Forwarder, webhost string, duration int) proxy.Dialer {
+	return &dhDialer{rrDialer: newRRDialer(dialers, webhost, duration)}
+}
+
+func (dh *dhDialer) NextDialer(dstAddr string) proxy.Dialer {
+	fnv1a := fnv.New32a()
+	fnv1a.Write([]byte(dstAddr))
+	idx := fnv1a.Sum32() % uint32(len(dh.fwdrs))
+	return dh.fwdrs[idx]
+}
+
+func (dh *dhDialer) Dial(network, addr string) (net.Conn, error) {
+	return dh.NextDialer(addr).Dial(network, addr)
+}
+
+func (dh *dhDialer) DialUDP(network, addr string) (pc net.PacketConn, writeTo net.Addr, err error) {
+	return dh.NextDialer(addr).DialUDP(network, addr)
+}
diff --git a/strategy/ha.go b/strategy/ha.go
index 5bd2c4d..ff8d2a2 100644
--- a/strategy/ha.go
+++ b/strategy/ha.go
@@ -1,6 +1,8 @@
 package strategy
 
 import (
+	"net"
+
 	"github.com/nadoo/glider/proxy"
 )
 
@@ -19,3 +21,11 @@ func (ha *haDialer) NextDialer(dstAddr string) proxy.Dialer {
 	}
 	return d
 }
+
+func (ha *haDialer) Dial(network, addr string) (net.Conn, error) {
+	return ha.NextDialer(addr).Dial(network, addr)
+}
+
+func (ha *haDialer) DialUDP(network, addr string) (pc net.PacketConn, writeTo net.Addr, err error) {
+	return ha.NextDialer(addr).DialUDP(network, addr)
+}
diff --git a/strategy/lha.go b/strategy/lha.go
index 8c0169f..0e897d7 100644
--- a/strategy/lha.go
+++ b/strategy/lha.go
@@ -1,6 +1,8 @@
 package strategy
 
 import (
+	"net"
+
 	"github.com/nadoo/glider/proxy"
 )
 
@@ -34,3 +36,11 @@ func (lha *lhaDialer) NextDialer(dstAddr string) proxy.Dialer {
 	lha.SetIndex(idx)
 	return lha.fwdrs[idx]
 }
+
+func (lha *lhaDialer) Dial(network, addr string) (net.Conn, error) {
+	return lha.NextDialer(addr).Dial(network, addr)
+}
+
+func (lha *lhaDialer) DialUDP(network, addr string) (pc net.PacketConn, writeTo net.Addr, err error) {
+	return lha.NextDialer(addr).DialUDP(network, addr)
+}
diff --git a/strategy/strategy.go b/strategy/strategy.go
index 21781a2..dcfe5bb 100644
--- a/strategy/strategy.go
+++ b/strategy/strategy.go
@@ -54,6 +54,9 @@ func NewDialer(s []string, c *Config) proxy.Dialer {
 	case "lha":
 		dialer = newLHADialer(fwdrs, c.CheckWebSite, c.CheckInterval)
 		log.F("forward to remote servers in latency based high availability mode.")
+	case "dh":
+		dialer = newDHDialer(fwdrs, c.CheckWebSite, c.CheckInterval)
+		log.F("forward to remote servers in destination hashing mode.")
 	default:
 		log.F("not supported forward mode '%s', just use the first forward server.", c.Strategy)
 		dialer = fwdrs[0]