skel.CmdArgs数据结构如下所示：
type CmdArgs struct {
ContainerID string
Netns string
IfName string
Args string
Path string
StdinData []byte
}
// cni/plugins/ipam/host-local/main.go
1、func cmdAdd(args *skel.CmdArgs) error
1、调用ipamConf, confVersion, err := allocator.LoadIPAMConfig(args.StdinData, args.Args)加载IPAM的配置和版本号
2、若ipamConf.ResolvConf不为""，则调用dns, err := parseResolvConf(ipamConf.ResolvConf)，并且将result.DNS = *dns
3、调用store, err := disk.New(ipamConf.Name, ipamConf.DataDir)
4、调用allocs := []*allocator.IPAllocator{} 获取allocator，保持该结构，当出错的时候，可以将所有IP地址释放
5、创建requestedIPs := map[string]net.IP{}并将ipamConf.IPArgs中的地址都填入其中
6、遍历for idx, ipRange := range ipamConf.Ranges，调用allocator := allocator.NewIPAllocator(ipamConf.Name, ipRange, store)
7、遍历requestedIPs，for k, ip := range requestedIPs，如果ipRange.IPInRange(ip)为nil，则说明请求的ip在可分配的地址范围内，
设置requestedIP = ip，并调用delete(requestedIPs, k)
8、调用ipConf, err := allocator.Get(args.ContainerID, requestedIP)，并调用allocs = append(allocs, allocator)和result.IPs = append(result.IPs, ipConf)
9、如果最后len(requestedIPs)不为0，则释放所有的allocator并报错
10、设置result.Routes = ipamConf.Routes
11、最后return types.PrintResult(result, confVersion)
// cni/plugins/ipam/host-local/backend/allocator/config.go
// NewIPAMConfig creates a NetworkConfig from the given network name.
2、func LoadIPAMConfig(bytes []byte, envArgs string) (*IPAMConfig, string, error)
1、首先设置n := Net{}，再调用json.Unmarshal(bytes, &n)进行解析
2、如果envArgs不为""，或者n.Args不为nil，则将他们都添加到n.IPAM.IPArgs中
3、如果n.IPAM.Range不为nil，说明使用的是老的配置方式，将n.IPAM.Range迁移到n.IPAM.Ranges中
4、遍历n.IPAM.Ranges，对IPv4或IPv6的range进行计数，若他们的数目大于1，切cni版本小于0.3.0则报错
5、检测各个range之间是否有重合
6、将n.IPAM.Name赋值为n.Name
7、最后return n.IPAM, n.CNIVersion, nil
Net数据结构如下所示：
type Net struct {
Name string
CNIVersion string
IPAM *IPAMConfig
Args *struct {
A *IPAMArgs
}
}
IPAMConfig数据结构如下所示：
// IPAMConfig represents the IP related network configuration
// 保留Range是为了向后兼容
type IPAMConfig struct {
*Range
Name string
Type string
Routes []*types.Route
DataDir string
ResolvConf string
Ranges []Range
IPArgs []net.IP // Requested IPs from CNI_ARGS and args
}
Range结构如下所示：
type Range struct {
RangeStart net.IP
RangeEnd net.IP
Subnet types.IPNet
Gateway net.IP
}
IPAMArgs结构如下所示：
type IPAMArgs struct {
IPs []net.IP
}
// cni/plugins/ipam/host-local/backend/disk/backend.go
3、func New(network, dataDir string) (*Store, error)
1、若dataDir为""，设置defaultDataDir为"/var/lib/cni/networks"
2、调用dir := filepath.Join(dataDir, network)并且调用os.MkdirAll(dir, 0755)创建目录
3、调用lk, err := NewFileLock(dir)
4、最后返回return &Store{*lk, dir}, nil
Store数据结构如下所示：
type Store struct {
FileLock // FileLock wraps os.File to be used as a lock using flock
dataDir string // 默认为/var/lib/cni/networks/NETWORKNAME
}
// cni/plugins/ipam/host-local/backend/allocator/allocator.go
4、func NewIPAllocator(netName string, r Range, store backend.Store) *IPAllocator
1、调用rangeID := base64.URLEncoding.EncodeToString(r.RangeStart)
2、返回return &IPAllocator{......}
IPAllocator数据结构如下所示：
type IPAllocator struct {
netName string
ipRange Range
store backend.Store
rangeID string // Used for tracking last reserved ip
}
// cni/plugins/ipam/host-local/backend/allocator/allocator.go
5、func (a *IPAllocator) Get(id string, requestedIP net.IP) (*current.IPConfig, error)
1、调用gw := a.ipRange
2、如果requestedIP 不为nil，首先判断requestedIP和gw不能相等，否则报错
如果a.ipRange.IPInRange(requestedIP)返回错误，则报错，否则调用reserved, err := a.store.Reserve(id, requestedIP, a.rangeID)将结果保存
最后，设置reservedIP为requestedIP
3、如果requestedIP不为nil，先调用iter, err := a.GetIter()，再调用for循环遍历iter，获取下一个可用的IP，之后的动作和2中相同
4、最后返回return ¤t.IPConfig{....}, nil