Return friendlier errors on timeout

client.go

@@ -2,6 +2,7 @@ package dhcp4client
 
 import (
 	"bytes"
+	"fmt"
 	"hash/fnv"
 	"math/rand"
 	"net"
@@ -143,6 +144,15 @@ func (c *Client) SendDiscoverPacket() (dhcp4.Packet, error) {
 	return discoveryPacket, c.SendPacket(discoveryPacket)
 }
 
+// TimeoutError records a timeout when waiting for a DHCP packet.
+type TimeoutError struct {
+	Timeout time.Duration
+}
+
+func (te *TimeoutError) Error() string {
+	return fmt.Sprintf("no DHCP packet received within %v", te.Timeout)
+}
+
 //Retreive Offer...
 //Wait for the offer for a specific Discovery Packet.
 func (c *Client) GetOffer(discoverPacket *dhcp4.Packet) (dhcp4.Packet, error) {
@@ -151,12 +161,15 @@ func (c *Client) GetOffer(discoverPacket *dhcp4.Packet) (dhcp4.Packet, error) {
 	for {
 		timeout := c.timeout - time.Since(start)
 		if timeout < 0 {
-			return dhcp4.Packet{}, syscall.ETIMEDOUT
+			return dhcp4.Packet{}, &TimeoutError{Timeout: c.timeout}
 		}
 
 		c.connection.SetReadTimeout(timeout)
 		readBuffer, source, err := c.connection.ReadFrom()
 		if err != nil {
+			if errno, ok := err.(syscall.Errno); ok && errno == syscall.EAGAIN {
+				return dhcp4.Packet{}, &TimeoutError{Timeout: c.timeout}
+			}
 			return dhcp4.Packet{}, err
 		}
 
@@ -199,12 +212,15 @@ func (c *Client) GetAcknowledgement(requestPacket *dhcp4.Packet) (dhcp4.Packet,
 	for {
 		timeout := c.timeout - time.Since(start)
 		if timeout < 0 {
-			return dhcp4.Packet{}, syscall.ETIMEDOUT
+			return dhcp4.Packet{}, &TimeoutError{Timeout: c.timeout}
 		}
 
 		c.connection.SetReadTimeout(timeout)
 		readBuffer, source, err := c.connection.ReadFrom()
 		if err != nil {
+			if errno, ok := err.(syscall.Errno); ok && errno == syscall.EAGAIN {
+				return dhcp4.Packet{}, &TimeoutError{Timeout: c.timeout}
+			}
 			return dhcp4.Packet{}, err
 		}