Commits on Aug 16, 2021

1. datapath: panic explicitly when IP of direct-routing-device not found …

   A user reported the follow panic on agent startup:
   
   ```
   level=info msg="  --devices=''" subsys=daemon
   level=info msg="  --direct-routing-device='wg0'" subsys=daemon
   ...
   level=info msg="Trying to auto-enable \"enable-node-port\", \"enable-external-ips\", \"enable-host-reachable-services\", \"enable-host-port\", \"enable-session-affinity\" features" subsys=daemon
   ...
   level=info msg="Cluster-ID is not specified, skipping ClusterMesh initialization" subsys=daemon
   panic: runtime error: index out of range [3] with length 0
   
   goroutine 1 [running]:
   encoding/binary.bigEndian.Uint32(...)
           /usr/local/go/src/encoding/binary/binary.go:112
   github.com/cilium/cilium/pkg/byteorder.HostSliceToNetwork(0x0, 0x0, 0x0, 0xa, 0x4795aa0, 0x41983f8)
           /go/src/github.com/cilium/cilium/pkg/byteorder/byteorder.go:134 +0x24f
   github.com/cilium/cilium/pkg/datapath/linux/config.(*HeaderfileWriter).WriteNodeConfig(0x4792cf0, 0x2e86b00, 0xc0005b4fe8, 0xc0000fcc68, 0x0, 0x0)
           /go/src/github.com/cilium/cilium/pkg/datapath/linux/config/config.go:426 +0x47db
   github.com/cilium/cilium/daemon/cmd.(*Daemon).createNodeConfigHeaderfile(0xc0001d5200, 0x0, 0x0)
           /go/src/github.com/cilium/cilium/daemon/cmd/datapath.go:72 +0x3e9
   github.com/cilium/cilium/daemon/cmd.(*Daemon).init(0xc0001d5200, 0x4239c20, 0x42278e0)
           /go/src/github.com/cilium/cilium/daemon/cmd/daemon.go:233 +0x6a6
   ```
   
   With some investigations, this is how the panic happened:
   
   1. --devices='' && --direct-routing-device='wg0' resulted in final option.Config.Devices=["eth0"] on his machine; which further led to
   2. no ip address were initialized in NodePort IPv4 address map for `wg0`, then
   3. `nodePortIPv4Addrs["wg0"]` returned an empty net.IP object, and the subsequent byteorder convertion paniced as above
   
   Although it's the user to blame for misconfiguration, the panic message
   is not so friendly either for ordinary users determining what's happened
   and how to fix it.
   
   This patch improves it by checking the existance of the IP address
   before using it, and panic explicitly with more user-friendly messages.
   
   Update: this patch also helps even if c042c05 is added recently, as
   the latter also accesses indexes before checking IP existance:
   
   ```go
   10 // NetIPv4ToHost32 converts an net.IP to a uint32 in host byte order. ip
   11 // must be a IPv4 address, otherwise the function will panic.
   12 func NetIPv4ToHost32(ip net.IP) uint32 {
   13     ipv4 := ip.To4()
   14     _ = ipv4[3] // Assert length of ipv4.
   15     return Native.Uint32(ipv4)
   16 }
   ```
   
   Signed-off-by: ArthurChiao <arthurchiao@hotmail.com>

   

   ArthurChiao committed Aug 16, 2021
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