kubernetes apiserver源码: apiserver service ip地址选定

零敲碎打，积少成多！

获取网段的地址池大小

package main

import (
	"fmt"
	"math"
	"net"
)

func main()  {
	size:=RangeSize(&net.IPNet{IP: net.ParseIP("10.0.0.0"), Mask: net.CIDRMask(24, 32)})
	fmt.Println(size) // => 256
}

// RangeSize returns the size of a range in valid addresses.
// returns the size of the subnet (or math.MaxInt64 if the range size would overflow int64)
func RangeSize(subnet *net.IPNet) int64 {
	ones, bits := subnet.Mask.Size()
	if bits == 32 && (bits-ones) >= 31 || bits == 128 && (bits-ones) >= 127 {
		return 0
	}
	// this checks that we are not overflowing an int64
	if bits-ones >= 63 {
		return math.MaxInt64
	}
	return int64(1) << uint(bits-ones)
}

从地址池获取IP

package main

import (
	"fmt"
	"math/big"
	"net"
)

func main()  {
	subnet:=&net.IPNet{IP: net.ParseIP("10.0.0.0"), Mask: net.CIDRMask(24, 32)}
        // 获取地址池第一个IP
	firstIpInPool,err:=GetIndexedIP(subnet,1)
	if err != nil {
		fmt.Println(err.Error())
		return
	}
	fmt.Println(firstIpInPool)
}

// BigForIP creates a big.Int based on the provided net.IP
func BigForIP(ip net.IP) *big.Int {
	// NOTE: Convert to 16-byte representation so we can
	// handle v4 and v6 values the same way.
	return big.NewInt(0).SetBytes(ip.To16())
}

// AddIPOffset adds the provided integer offset to a base big.Int representing a net.IP
// NOTE: If you started with a v4 address and overflow it, you get a v6 result.
func AddIPOffset(base *big.Int, offset int) net.IP {
	r := big.NewInt(0).Add(base, big.NewInt(int64(offset))).Bytes()
	r = append(make([]byte, 16), r...)
	return net.IP(r[len(r)-16:])
}
// GetIndexedIP returns a net.IP that is subnet.IP + index in the contiguous IP space.
func GetIndexedIP(subnet *net.IPNet, index int) (net.IP, error) {
	ip := AddIPOffset(BigForIP(subnet.IP), index)
	if !subnet.Contains(ip) {
		return nil, fmt.Errorf("can't generate IP with index %d from subnet. subnet too small. subnet: %q", index, subnet)
	}
	return ip, nil
}

kubernetes service ip选定

service ip 范围是kubernetes分配给Service的服务IP地址。

• pkg/controlplane/services.go

// ServiceIPRange checks if the serviceClusterIPRange flag is nil, raising a warning if so and
// setting service ip range to the default value in kubeoptions.DefaultServiceIPCIDR
// for now until the default is removed per the deprecation timeline guidelines.
// Returns service ip range, api server service IP, and an error
func ServiceIPRange(passedServiceClusterIPRange net.IPNet) (net.IPNet, net.IP, error) {
        // 检查是否为空，如果为空，默认设置api server service为10.0.0.1
	serviceClusterIPRange := passedServiceClusterIPRange
	if passedServiceClusterIPRange.IP == nil {
		klog.Warningf("No CIDR for service cluster IPs specified. Default value which was %s is deprecated and will be removed in future releases. Please specify it using --service-cluster-ip-range on kube-apiserver.", kubeoptions.DefaultServiceIPCIDR.String())
		serviceClusterIPRange = kubeoptions.DefaultServiceIPCIDR
	}
        // 检查service ip 地址池大小 大于 8
	size := integer.Int64Min(utilnet.RangeSize(&serviceClusterIPRange), 1<<16)
	if size < 8 {
		return net.IPNet{}, net.IP{}, fmt.Errorf("the service cluster IP range must be at least %d IP addresses", 8)
	}

	// Select the first valid IP from ServiceClusterIPRange to use as the GenericAPIServer service IP.
	apiServerServiceIP, err := utilnet.GetIndexedIP(&serviceClusterIPRange, 1)
	if err != nil {
		return net.IPNet{}, net.IP{}, err
	}
	klog.V(4).Infof("Setting service IP to %q (read-write).", apiServerServiceIP)

	return serviceClusterIPRange, apiServerServiceIP, nil
}