Claim address requested by caller

api/ipam.go

@@ -32,6 +32,12 @@ func (client *Client) LookupIP(ID string) (*net.IPNet, error) {
 	return client.ipamOp(ID, "GET")
 }
 
+// Claim a specific IP on behalf of the ID
+func (client *Client) ClaimIP(ID string, addr net.IP) error {
+	_, err := client.httpVerb("PUT", fmt.Sprintf("/ip/%s/%s", ID, addr), nil)
+	return err
+}
+
 // release an IP which is no longer needed
 func (client *Client) ReleaseIP(ID string) error {
 	_, err := client.ipamOp(ID, "DELETE")

ipam/claim.go

@@ -75,6 +75,9 @@ func (c *claim) Try(alloc *Allocator) bool {
 	case "":
 		if err := alloc.space.Claim(c.addr); err == nil {
 			alloc.debugln("Claimed", c.addr, "for", c.ident)
+			if c.ident == "_" { // Special "I don't have a unique ID" identifier
+				c.ident = c.addr.String()
+			}
 			alloc.addOwned(c.ident, c.addr)
 			c.sendResult(nil)
 		} else {
@@ -84,6 +87,9 @@ func (c *claim) Try(alloc *Allocator) bool {
 		// same identifier is claiming same address; that's OK
 		alloc.debugln("Re-Claimed", c.addr, "for", c.ident)
 		c.sendResult(nil)
+	case c.addr.String():
+		// Address already allocated via "_" name
+		c.sendResult(fmt.Errorf("address %s already in use", c.addr))
 	default:
 		// Addr already owned by container on this machine
 		c.sendResult(fmt.Errorf("address %s is already owned by %s", c.addr.String(), existingIdent))

plugin/ipam/driver.go

@@ -78,14 +78,21 @@ func (i *ipam) RequestAddress(poolID string, address net.IP, options map[string]
 	if _, subnet, err = net.ParseCIDR(parts[1]); err != nil {
 		return
 	}
-	if _, iprange, err = net.ParseCIDR(parts[2]); err != nil {
-		return
-	}
-	// We are lying slightly to IPAM here: the range is not a subnet
-	if ip, err = i.weave.AllocateIPInSubnet("_", iprange); err != nil {
-		return
+	if address != nil { // try to claim specific address requested
+		if err = i.weave.ClaimIP("_", address); err != nil {
+			return
+		}
+		ip = &net.IPNet{IP: address, Mask: subnet.Mask}
+	} else {
+		if _, iprange, err = net.ParseCIDR(parts[2]); err != nil {
+			return
+		}
+		// We are lying slightly to IPAM here: the range is not a subnet
+		if ip, err = i.weave.AllocateIPInSubnet("_", iprange); err != nil {
+			return
+		}
+		ip.Mask = subnet.Mask // fix up the subnet we lied about
 	}
-	ip.Mask = subnet.Mask // fix up the subnet we lied about
 	return
 }