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/genericopt.go

@@ -0,0 +1,55 @@
+// 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.
+
+package ipv4
+
+// TOS returns the type-of-service field value for outgoing packets.
+func (c *genericOpt) TOS() (int, error) {
+	if !c.ok() {
+		return 0, errInvalidConn
+	}
+	so, ok := sockOpts[ssoTOS]
+	if !ok {
+		return 0, errNotImplemented
+	}
+	return so.GetInt(c.Conn)
+}
+
+// SetTOS sets the type-of-service field value for future outgoing
+// packets.
+func (c *genericOpt) SetTOS(tos int) error {
+	if !c.ok() {
+		return errInvalidConn
+	}
+	so, ok := sockOpts[ssoTOS]
+	if !ok {
+		return errNotImplemented
+	}
+	return so.SetInt(c.Conn, tos)
+}
+
+// TTL returns the time-to-live field value for outgoing packets.
+func (c *genericOpt) TTL() (int, error) {
+	if !c.ok() {
+		return 0, errInvalidConn
+	}
+	so, ok := sockOpts[ssoTTL]
+	if !ok {
+		return 0, errNotImplemented
+	}
+	return so.GetInt(c.Conn)
+}
+
+// SetTTL sets the time-to-live field value for future outgoing
+// packets.
+func (c *genericOpt) SetTTL(ttl int) error {
+	if !c.ok() {
+		return errInvalidConn
+	}
+	so, ok := sockOpts[ssoTTL]
+	if !ok {
+		return errNotImplemented
+	}
+	return so.SetInt(c.Conn, ttl)
+}