allocators: Export an error for no address available

This is a sentinel error that downstream users should be able to compare
against to identify when the allocator is out of addresses, move it from
the bitmap allocator package to the general allocator interface package

Signed-off-by: Anatole Denis <anatole@unverle.fr>

plugins/allocators/allocator.go

@@ -8,6 +8,7 @@
 package allocators
 
 import (
+	"errors"
 	"fmt"
 	"net"
 )
@@ -42,3 +43,6 @@ type ErrDoubleFree struct {
 func (err *ErrDoubleFree) Error() string {
 	return fmt.Sprint("Attempted to free unallocated block at ", err.Loc.String())
 }
+
+// ErrNoAddrAvail is returned when we can't allocate an IP because there's no unallocated space left
+var ErrNoAddrAvail = errors.New("no address available to allocate")

plugins/allocators/bitmap/bitmap.go

@@ -75,7 +75,7 @@ func (a *Allocator) Allocate(hint net.IPNet) (ret net.IPNet, err error) {
 	// Find a free prefix
 	next, ok := a.bitmap.NextClear(0)
 	if !ok {
-		err = errors.New("No prefix available")
+		err = allocators.ErrNoAddrAvail
 		return
 	}
 	a.bitmap.Set(next)

plugins/allocators/bitmap/bitmap_ipv4.go

@@ -19,13 +19,8 @@ import (
 )
 
 var (
-	// ErrNoAddrAvail is returned when we can't allocate an IP
-	// because there's no unallocated space left
-	ErrNoAddrAvail = errors.New("No address available to allocate")
-
-	errNotInRange = errors.New("IP outside of allowed range")
-
-	errInvalidIP = errors.New("Invalid IP passed as input")
+	errNotInRange = errors.New("IPv4 address outside of allowed range")
+	errInvalidIP  = errors.New("invalid IPv4 address passed as input")
 )
 
 // IPv4Allocator allocates IPv4 addresses, tracking utilization with a bitmap
@@ -33,16 +28,18 @@ type IPv4Allocator struct {
 	start uint32
 	end   uint32
 
+	// This bitset implementation isn't goroutine-safe, we protect it with a mutex for now
+	// until we can swap for another concurrent implementation
 	bitmap *bitset.BitSet
 	l      sync.Mutex
 }
 
 func (a *IPv4Allocator) toIP(offset uint32) net.IP {
 	if offset > a.end-a.start {
-		return nil
+		panic("BUG: offset out of bounds")
 	}
 
-	r := make(net.IP, 4)
+	r := make(net.IP, net.IPv4len)
 	binary.BigEndian.PutUint32(r, a.start+offset)
 	return r
 }
@@ -78,7 +75,7 @@ func (a *IPv4Allocator) Allocate(hint net.IPNet) (n net.IPNet, err error) {
 		// Then any available address
 		avail, ok := a.bitmap.NextClear(0)
 		if !ok {
-			return n, ErrNoAddrAvail
+			return n, allocators.ErrNoAddrAvail
 		}
 		next = avail
 	}
@@ -108,7 +105,7 @@ func (a *IPv4Allocator) Free(n net.IPNet) error {
 // NewIPv4Allocator creates a new allocator suitable for giving out IPv4 addresses
 func NewIPv4Allocator(start, end net.IP) (*IPv4Allocator, error) {
 	if start.To4() == nil || end.To4() == nil {
-		return nil, fmt.Errorf("Invalid IPv4s given to create the allocator: [%s,%s]", start, end)
+		return nil, fmt.Errorf("invalid IPv4 addresses given to create the allocator: [%s,%s]", start, end)
 	}
 
 	alloc := IPv4Allocator{
@@ -117,7 +114,7 @@ func NewIPv4Allocator(start, end net.IP) (*IPv4Allocator, error) {
 	}
 
 	if alloc.start > alloc.end {
-		return nil, errors.New("No IPs in the given range to allocate")
+		return nil, errors.New("no IPs in the given range to allocate")
 	}
 	alloc.bitmap = bitset.New(uint(alloc.end - alloc.start + 1))