From b09b5567961636836e9daf5350f4910a8ee2d793 Mon Sep 17 00:00:00 2001
From: Adam Harrison <harrisonadamw@gmail.com>
Date: Fri, 5 Feb 2016 15:31:09 +0000
Subject: [PATCH] Utility function to configure ARP cache timers

---
 common/arp.go | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 common/arp.go

diff --git a/common/arp.go b/common/arp.go
new file mode 100644
index 00000000..094d6b16
--- /dev/null
+++ b/common/arp.go
@@ -0,0 +1,43 @@
+package common
+
+import "fmt"
+import "io"
+import "os"
+
+// Configure the ARP cache parameters for the given interface.  This
+// makes containers react more quickly to a change in the MAC address
+// associated with an IP address.
+func ConfigureARPCache(name string) error {
+	if err := sysctl(fmt.Sprintf("net/ipv4/neigh/%s/base_reachable_time", name), "5"); err != nil {
+		return err
+	}
+	if err := sysctl(fmt.Sprintf("net/ipv4/neigh/%s/delay_first_probe_time", name), "2"); err != nil {
+		return err
+	}
+	if err := sysctl(fmt.Sprintf("net/ipv4/neigh/%s/ucast_solicit", name), "1"); err != nil {
+		return err
+	}
+	return nil
+}
+
+func sysctl(variable, value string) error {
+	f, err := os.OpenFile(fmt.Sprintf("/proc/sys/%s", variable), os.O_WRONLY, 0)
+	if err != nil {
+		return err
+	}
+
+	n, err := io.WriteString(f, value)
+	if err != nil {
+		return err
+	}
+	if n < len(value) {
+		return io.ErrShortWrite
+	}
+
+	err = f.Close()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}