Use caddy's certmagic library for extensible/robust ACME handling (#14177)

* use certmagic for more extensible/robust ACME cert handling

* accept TOS based on config option

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/golang.org/x/net/ipv4/control_bsd.go

@@ -0,0 +1,41 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build aix darwin dragonfly freebsd netbsd openbsd
+
+package ipv4
+
+import (
+	"net"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/net/internal/iana"
+	"golang.org/x/net/internal/socket"
+)
+
+func marshalDst(b []byte, cm *ControlMessage) []byte {
+	m := socket.ControlMessage(b)
+	m.MarshalHeader(iana.ProtocolIP, sysIP_RECVDSTADDR, net.IPv4len)
+	return m.Next(net.IPv4len)
+}
+
+func parseDst(cm *ControlMessage, b []byte) {
+	if len(cm.Dst) < net.IPv4len {
+		cm.Dst = make(net.IP, net.IPv4len)
+	}
+	copy(cm.Dst, b[:net.IPv4len])
+}
+
+func marshalInterface(b []byte, cm *ControlMessage) []byte {
+	m := socket.ControlMessage(b)
+	m.MarshalHeader(iana.ProtocolIP, sysIP_RECVIF, syscall.SizeofSockaddrDatalink)
+	return m.Next(syscall.SizeofSockaddrDatalink)
+}
+
+func parseInterface(cm *ControlMessage, b []byte) {
+	var sadl syscall.SockaddrDatalink
+	copy((*[unsafe.Sizeof(sadl)]byte)(unsafe.Pointer(&sadl))[:], b)
+	cm.IfIndex = int(sadl.Index)
+}