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/sys_asmreq.go

@@ -0,0 +1,122 @@
+// 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 solaris windows
+
+package ipv4
+
+import (
+	"errors"
+	"net"
+	"unsafe"
+
+	"golang.org/x/net/internal/socket"
+)
+
+var errNoSuchInterface = errors.New("no such interface")
+
+func (so *sockOpt) setIPMreq(c *socket.Conn, ifi *net.Interface, grp net.IP) error {
+	mreq := ipMreq{Multiaddr: [4]byte{grp[0], grp[1], grp[2], grp[3]}}
+	if err := setIPMreqInterface(&mreq, ifi); err != nil {
+		return err
+	}
+	b := (*[sizeofIPMreq]byte)(unsafe.Pointer(&mreq))[:sizeofIPMreq]
+	return so.Set(c, b)
+}
+
+func (so *sockOpt) getMulticastIf(c *socket.Conn) (*net.Interface, error) {
+	var b [4]byte
+	if _, err := so.Get(c, b[:]); err != nil {
+		return nil, err
+	}
+	ifi, err := netIP4ToInterface(net.IPv4(b[0], b[1], b[2], b[3]))
+	if err != nil {
+		return nil, err
+	}
+	return ifi, nil
+}
+
+func (so *sockOpt) setMulticastIf(c *socket.Conn, ifi *net.Interface) error {
+	ip, err := netInterfaceToIP4(ifi)
+	if err != nil {
+		return err
+	}
+	var b [4]byte
+	copy(b[:], ip)
+	return so.Set(c, b[:])
+}
+
+func setIPMreqInterface(mreq *ipMreq, ifi *net.Interface) error {
+	if ifi == nil {
+		return nil
+	}
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		return err
+	}
+	for _, ifa := range ifat {
+		switch ifa := ifa.(type) {
+		case *net.IPAddr:
+			if ip := ifa.IP.To4(); ip != nil {
+				copy(mreq.Interface[:], ip)
+				return nil
+			}
+		case *net.IPNet:
+			if ip := ifa.IP.To4(); ip != nil {
+				copy(mreq.Interface[:], ip)
+				return nil
+			}
+		}
+	}
+	return errNoSuchInterface
+}
+
+func netIP4ToInterface(ip net.IP) (*net.Interface, error) {
+	ift, err := net.Interfaces()
+	if err != nil {
+		return nil, err
+	}
+	for _, ifi := range ift {
+		ifat, err := ifi.Addrs()
+		if err != nil {
+			return nil, err
+		}
+		for _, ifa := range ifat {
+			switch ifa := ifa.(type) {
+			case *net.IPAddr:
+				if ip.Equal(ifa.IP) {
+					return &ifi, nil
+				}
+			case *net.IPNet:
+				if ip.Equal(ifa.IP) {
+					return &ifi, nil
+				}
+			}
+		}
+	}
+	return nil, errNoSuchInterface
+}
+
+func netInterfaceToIP4(ifi *net.Interface) (net.IP, error) {
+	if ifi == nil {
+		return net.IPv4zero.To4(), nil
+	}
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		return nil, err
+	}
+	for _, ifa := range ifat {
+		switch ifa := ifa.(type) {
+		case *net.IPAddr:
+			if ip := ifa.IP.To4(); ip != nil {
+				return ip, nil
+			}
+		case *net.IPNet:
+			if ip := ifa.IP.To4(); ip != nil {
+				return ip, nil
+			}
+		}
+	}
+	return nil, errNoSuchInterface
+}