Bind DNS names through /etc/hosts

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

pkg/weave/weave.go

@@ -0,0 +1,131 @@
+// Copyright Weaveworks
+// github.com/weaveworks/weave/net
+
+package weave
+
+import (
+	"fmt"
+	"net"
+	"os"
+
+	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netns"
+)
+
+type Dev struct {
+	Name  string           `json:"Name,omitempty"`
+	MAC   net.HardwareAddr `json:"MAC,omitempty"`
+	CIDRs []*net.IPNet     `json:"CIDRs,omitempty"`
+}
+
+func linkToNetDev(link netlink.Link) (Dev, error) {
+	addrs, err := netlink.AddrList(link, netlink.FAMILY_V4)
+	if err != nil {
+		return Dev{}, err
+	}
+
+	netDev := Dev{Name: link.Attrs().Name, MAC: link.Attrs().HardwareAddr}
+	for _, addr := range addrs {
+		netDev.CIDRs = append(netDev.CIDRs, addr.IPNet)
+	}
+	return netDev, nil
+}
+
+// ConnectedToBridgeVethPeerIds returns peer indexes of veth links connected to
+// the given bridge. The peer index is used to query from a container netns
+// whether the container is connected to the bridge.
+func ConnectedToBridgeVethPeerIds(bridgeName string) ([]int, error) {
+	var ids []int
+
+	br, err := netlink.LinkByName(bridgeName)
+	if err != nil {
+		return nil, err
+	}
+	links, err := netlink.LinkList()
+	if err != nil {
+		return nil, err
+	}
+
+	for _, link := range links {
+		if _, isveth := link.(*netlink.Veth); isveth && link.Attrs().MasterIndex == br.Attrs().Index {
+			peerID := link.Attrs().ParentIndex
+			if peerID == 0 {
+				// perhaps running on an older kernel where ParentIndex doesn't work.
+				// as fall-back, assume the peers are consecutive
+				peerID = link.Attrs().Index - 1
+			}
+			ids = append(ids, peerID)
+		}
+	}
+
+	return ids, nil
+}
+
+// Lookup the weave interface of a container
+func GetWeaveNetDevs(processID int) ([]Dev, error) {
+	peerIDs, err := ConnectedToBridgeVethPeerIds("weave")
+	if err != nil {
+		return nil, err
+	}
+
+	return GetNetDevsByVethPeerIds(processID, peerIDs)
+}
+
+func GetNetDevsByVethPeerIds(processID int, peerIDs []int) ([]Dev, error) {
+	// Bail out if this container is running in the root namespace
+	netnsRoot, err := netns.GetFromPid(1)
+	if err != nil {
+		return nil, fmt.Errorf("unable to open root namespace: %s", err)
+	}
+	defer netnsRoot.Close()
+	netnsContainer, err := netns.GetFromPid(processID)
+	if err != nil {
+		// Unable to find a namespace for this process - just return nothing
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("unable to open process %d namespace: %s", processID, err)
+	}
+	defer netnsContainer.Close()
+	if netnsRoot.Equal(netnsContainer) {
+		return nil, nil
+	}
+
+	// convert list of peerIDs into a map for faster lookup
+	indexes := make(map[int]struct{})
+	for _, id := range peerIDs {
+		indexes[id] = struct{}{}
+	}
+
+	var netdevs []Dev
+	err = WithNetNS(netnsContainer, func() error {
+		links, err := netlink.LinkList()
+		if err != nil {
+			return err
+		}
+
+		for _, link := range links {
+			if _, found := indexes[link.Attrs().Index]; found {
+				netdev, err := linkToNetDev(link)
+				if err != nil {
+					return err
+				}
+				netdevs = append(netdevs, netdev)
+			}
+		}
+		return nil
+	})
+
+	return netdevs, err
+}
+
+// Get the weave bridge interface.
+// NB: Should be called from the root network namespace.
+func GetBridgeNetDev(bridgeName string) (Dev, error) {
+	link, err := netlink.LinkByName(bridgeName)
+	if err != nil {
+		return Dev{}, err
+	}
+
+	return linkToNetDev(link)
+}