fix: fix dns on linux (#336)

* fix: fix dns on linux

* feat: detect run in Github action or not to setup DNS

vendor/github.com/tailscale/netlink/bpf_linux.go

@@ -0,0 +1,77 @@
+package netlink
+
+import (
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+type BpfProgType uint32
+
+const (
+	BPF_PROG_TYPE_UNSPEC BpfProgType = iota
+	BPF_PROG_TYPE_SOCKET_FILTER
+	BPF_PROG_TYPE_KPROBE
+	BPF_PROG_TYPE_SCHED_CLS
+	BPF_PROG_TYPE_SCHED_ACT
+	BPF_PROG_TYPE_TRACEPOINT
+	BPF_PROG_TYPE_XDP
+	BPF_PROG_TYPE_PERF_EVENT
+	BPF_PROG_TYPE_CGROUP_SKB
+	BPF_PROG_TYPE_CGROUP_SOCK
+	BPF_PROG_TYPE_LWT_IN
+	BPF_PROG_TYPE_LWT_OUT
+	BPF_PROG_TYPE_LWT_XMIT
+	BPF_PROG_TYPE_SOCK_OPS
+	BPF_PROG_TYPE_SK_SKB
+	BPF_PROG_TYPE_CGROUP_DEVICE
+	BPF_PROG_TYPE_SK_MSG
+	BPF_PROG_TYPE_RAW_TRACEPOINT
+	BPF_PROG_TYPE_CGROUP_SOCK_ADDR
+	BPF_PROG_TYPE_LWT_SEG6LOCAL
+	BPF_PROG_TYPE_LIRC_MODE2
+	BPF_PROG_TYPE_SK_REUSEPORT
+	BPF_PROG_TYPE_FLOW_DISSECTOR
+	BPF_PROG_TYPE_CGROUP_SYSCTL
+	BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE
+	BPF_PROG_TYPE_CGROUP_SOCKOPT
+	BPF_PROG_TYPE_TRACING
+	BPF_PROG_TYPE_STRUCT_OPS
+	BPF_PROG_TYPE_EXT
+	BPF_PROG_TYPE_LSM
+	BPF_PROG_TYPE_SK_LOOKUP
+)
+
+type BPFAttr struct {
+	ProgType    uint32
+	InsnCnt     uint32
+	Insns       uintptr
+	License     uintptr
+	LogLevel    uint32
+	LogSize     uint32
+	LogBuf      uintptr
+	KernVersion uint32
+}
+
+// loadSimpleBpf loads a trivial bpf program for testing purposes.
+func loadSimpleBpf(progType BpfProgType, ret uint32) (int, error) {
+	insns := []uint64{
+		0x00000000000000b7 | (uint64(ret) << 32),
+		0x0000000000000095,
+	}
+	license := []byte{'A', 'S', 'L', '2', '\x00'}
+	attr := BPFAttr{
+		ProgType: uint32(progType),
+		InsnCnt:  uint32(len(insns)),
+		Insns:    uintptr(unsafe.Pointer(&insns[0])),
+		License:  uintptr(unsafe.Pointer(&license[0])),
+	}
+	fd, _, errno := unix.Syscall(unix.SYS_BPF,
+		5, /* bpf cmd */
+		uintptr(unsafe.Pointer(&attr)),
+		unsafe.Sizeof(attr))
+	if errno != 0 {
+		return 0, errno
+	}
+	return int(fd), nil
+}