github.com/Prakhar-Agarwal-byte/moby@v0.0.0-20231027092010-a14e3e8ab87e/libnetwork/drivers/bridge/setup_ipv4_linux.go (about)

     1  package bridge
     2  
     3  import (
     4  	"context"
     5  	"errors"
     6  	"fmt"
     7  	"net"
     8  	"os"
     9  	"path/filepath"
    10  
    11  	"github.com/containerd/log"
    12  	"github.com/Prakhar-Agarwal-byte/moby/libnetwork/types"
    13  	"github.com/vishvananda/netlink"
    14  )
    15  
    16  func selectIPv4Address(addresses []netlink.Addr, selector *net.IPNet) (netlink.Addr, error) {
    17  	if len(addresses) == 0 {
    18  		return netlink.Addr{}, errors.New("unable to select an address as the address pool is empty")
    19  	}
    20  	if selector != nil {
    21  		for _, addr := range addresses {
    22  			if selector.Contains(addr.IP) {
    23  				return addr, nil
    24  			}
    25  		}
    26  	}
    27  	return addresses[0], nil
    28  }
    29  
    30  func setupBridgeIPv4(config *networkConfiguration, i *bridgeInterface) error {
    31  	// TODO(aker): the bridge driver panics if its bridgeIPv4 field isn't set. Once bridge subnet and bridge IP address
    32  	//             are decoupled, we should assign it only when it's really needed.
    33  	i.bridgeIPv4 = config.AddressIPv4
    34  
    35  	if config.Internal {
    36  		return nil
    37  	}
    38  
    39  	if !config.InhibitIPv4 {
    40  		addrv4List, _, err := i.addresses()
    41  		if err != nil {
    42  			return fmt.Errorf("failed to retrieve bridge interface addresses: %v", err)
    43  		}
    44  
    45  		addrv4, _ := selectIPv4Address(addrv4List, config.AddressIPv4)
    46  
    47  		if !types.CompareIPNet(addrv4.IPNet, config.AddressIPv4) {
    48  			if addrv4.IPNet != nil {
    49  				if err := i.nlh.AddrDel(i.Link, &addrv4); err != nil {
    50  					return fmt.Errorf("failed to remove current ip address from bridge: %v", err)
    51  				}
    52  			}
    53  			log.G(context.TODO()).Debugf("Assigning address to bridge interface %s: %s", config.BridgeName, config.AddressIPv4)
    54  			if err := i.nlh.AddrAdd(i.Link, &netlink.Addr{IPNet: config.AddressIPv4}); err != nil {
    55  				return &IPv4AddrAddError{IP: config.AddressIPv4, Err: err}
    56  			}
    57  		}
    58  	}
    59  
    60  	// Store the default gateway
    61  	i.gatewayIPv4 = config.AddressIPv4.IP
    62  
    63  	return nil
    64  }
    65  
    66  func setupGatewayIPv4(config *networkConfiguration, i *bridgeInterface) error {
    67  	if !i.bridgeIPv4.Contains(config.DefaultGatewayIPv4) {
    68  		return &ErrInvalidGateway{}
    69  	}
    70  	if config.Internal {
    71  		return types.InvalidParameterErrorf("no gateway can be set on an internal bridge network")
    72  	}
    73  
    74  	// Store requested default gateway
    75  	i.gatewayIPv4 = config.DefaultGatewayIPv4
    76  
    77  	return nil
    78  }
    79  
    80  func setupLoopbackAddressesRouting(config *networkConfiguration, i *bridgeInterface) error {
    81  	sysPath := filepath.Join("/proc/sys/net/ipv4/conf", config.BridgeName, "route_localnet")
    82  	ipv4LoRoutingData, err := os.ReadFile(sysPath)
    83  	if err != nil {
    84  		return fmt.Errorf("Cannot read IPv4 local routing setup: %v", err)
    85  	}
    86  	// Enable loopback addresses routing only if it isn't already enabled
    87  	if ipv4LoRoutingData[0] != '1' {
    88  		if err := os.WriteFile(sysPath, []byte{'1', '\n'}, 0o644); err != nil {
    89  			return fmt.Errorf("Unable to enable local routing for hairpin mode: %v", err)
    90  		}
    91  	}
    92  	return nil
    93  }