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/ipv6/control_unix.go

@@ -0,0 +1,55 @@
+// Copyright 2013 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 linux netbsd openbsd solaris zos
+
+package ipv6
+
+import "golang.org/x/net/internal/socket"
+
+func setControlMessage(c *socket.Conn, opt *rawOpt, cf ControlFlags, on bool) error {
+	opt.Lock()
+	defer opt.Unlock()
+	if so, ok := sockOpts[ssoReceiveTrafficClass]; ok && cf&FlagTrafficClass != 0 {
+		if err := so.SetInt(c, boolint(on)); err != nil {
+			return err
+		}
+		if on {
+			opt.set(FlagTrafficClass)
+		} else {
+			opt.clear(FlagTrafficClass)
+		}
+	}
+	if so, ok := sockOpts[ssoReceiveHopLimit]; ok && cf&FlagHopLimit != 0 {
+		if err := so.SetInt(c, boolint(on)); err != nil {
+			return err
+		}
+		if on {
+			opt.set(FlagHopLimit)
+		} else {
+			opt.clear(FlagHopLimit)
+		}
+	}
+	if so, ok := sockOpts[ssoReceivePacketInfo]; ok && cf&flagPacketInfo != 0 {
+		if err := so.SetInt(c, boolint(on)); err != nil {
+			return err
+		}
+		if on {
+			opt.set(cf & flagPacketInfo)
+		} else {
+			opt.clear(cf & flagPacketInfo)
+		}
+	}
+	if so, ok := sockOpts[ssoReceivePathMTU]; ok && cf&FlagPathMTU != 0 {
+		if err := so.SetInt(c, boolint(on)); err != nil {
+			return err
+		}
+		if on {
+			opt.set(FlagPathMTU)
+		} else {
+			opt.clear(FlagPathMTU)
+		}
+	}
+	return nil
+}