From: 1vivy <1vivy@tutanota.com>
Date: Sat, 22 Jul 2023 13:07:10 -0600
Subject: wide-dhcpv6: T5387: Add a no release option '-n'.

This prevents a release signal from being sent to the ISP causing a new PD or address to be allocated.

Co-authored-by: MrLenin <909621+MrLenin@users.noreply.github.com>
Co-authored-by: marjohn56 <martin@queens-park.com>
--- wide-dhcpv6.orig/common.h
+++ wide-dhcpv6/common.h
@@ -120,6 +120,7 @@ sysdep_sa_len (const struct sockaddr *sa
 extern int foreground;
 extern int debug_thresh;
 extern char *device;
+extern int opt_norelease;
 
 /* search option for dhcp6_find_listval() */
 #define MATCHLIST_PREFIXLEN 0x1
--- wide-dhcpv6.orig/dhcp6c.8
+++ wide-dhcpv6/dhcp6c.8
@@ -88,6 +88,10 @@ is terminated.  (suits for a use in shel
 Since the configuration is internally generated, you cannot provide a configuration in this mode.  If you want to have different actions for the stateless DHCPv6 information, you should write an appropriate configuration and invoke
 .Nm
 without this option.
+.It Fl n
+Prevent Release message from being sent to DHCPv6 server when
+.Nm
+stops. This is useful for preventing a new address from being configured by the DHCPv6 server when restarting the DHCPv6 client.
 .It Fl p Ar pid-file
 Use
 .Ar pid-file
@@ -109,18 +113,22 @@ or
 .Fl i
 option is specified.
 .Pp
-Upon receipt of the
-.Dv SIGHUP
+Upon receipt of a
+.Dv SIGHUP ,
+.Dv SIGTERM ,
 or
-.Dv SIGTERM
-signals,
-.Nm
-will remove all stateful resources from the system.
-In the former case the daemon will then reinvoke itself,
-while it will stop running in the latter case.
-In either case,
+.Dv SIGUSR1
+signal,
 .Nm
-will send DHCPv6 Release messages to release resources assigned from servers.
+will remove all stateful resources from the system. After that,
+.Dv SIGHUP
+reinitializes the daemon, and
+.Dv SIGTERM
+stops the daemon. In both cases, DHCPv6 Release message will be sent to release resources assigned from servers.
+.Dv SIGUSR1
+stops the daemon as
+.Dv SIGTERM
+does though DHCPv6 Release message will not be sent.
 .\"
 .Sh FILES
 .Bl -tag -width /etc/wide-dhcpv6/dhcp6c.conf -compact
--- wide-dhcpv6.orig/dhcp6c.c
+++ wide-dhcpv6/dhcp6c.c
@@ -84,6 +84,7 @@ static int exit_ok = 0;
 static sig_atomic_t sig_flags = 0;
 #define SIGF_TERM 0x1
 #define SIGF_HUP 0x2
+#define SIGF_USR1 0x4
 
 const dhcp6_mode_t dhcp6_mode = DHCP6_MODE_CLIENT;
 
@@ -108,6 +109,8 @@ static int ctldigestlen;
 
 static int infreq_mode = 0;
 
+int opt_norelease;
+
 static inline int get_val32 __P((char **, int *, u_int32_t *));
 static inline int get_ifname __P((char **, int *, char *, int));
 
@@ -170,7 +173,7 @@ main(argc, argv)
 	else
 		progname++;
 
-	while ((ch = getopt(argc, argv, "c:dDfik:p:P:")) != -1) {
+	while ((ch = getopt(argc, argv, "c:dDfik:np:P:")) != -1) {
 		switch (ch) {
 		case 'c':
 			conffile = optarg;
@@ -190,6 +193,9 @@ main(argc, argv)
 		case 'k':
 			ctlkeyfile = optarg;
 			break;
+		case 'n':
+			opt_norelease = 1;
+			break;
 		case 'p':
 			pid_file = optarg;
 			break;
@@ -395,6 +401,11 @@ client6_init()
 		    strerror(errno));
 		exit(1);
 	}
+	if (signal(SIGUSR1, client6_signal) == SIG_ERR) {
+		debug_printf(LOG_WARNING, FNAME, "failed to set signal: %s",
+		    strerror(errno));
+		exit(1);
+	}
 }
 
 int
@@ -525,6 +536,13 @@ process_signals()
 		free_resources(NULL);
 		client6_startall(1);
 	}
+	if ((sig_flags & SIGF_USR1)) {
+		debug_printf(LOG_INFO, FNAME, "exit without release");
+		exit_ok = 1;
+		opt_norelease = 1;
+		free_resources(NULL);
+		check_exit();
+	}
 
 	sig_flags = 0;
 }
@@ -1171,6 +1189,9 @@ client6_signal(sig)
 	case SIGHUP:
 		sig_flags |= SIGF_HUP;
 		break;
+	case SIGUSR1:
+		sig_flags |= SIGF_USR1;
+		break;
 	}
 }
 
--- wide-dhcpv6.orig/dhcp6c_ia.c
+++ wide-dhcpv6/dhcp6c_ia.c
@@ -420,7 +420,13 @@ release_all_ia(ifp)
 		for (ia = TAILQ_FIRST(&iac->iadata); ia; ia = ia_next) {
 			ia_next = TAILQ_NEXT(ia, link);
 
-			(void)release_ia(ia);
+			if (opt_norelease == 0) {
+				debug_printf(LOG_INFO, FNAME, "Start address "
+				    "release");
+				(void)release_ia(ia);
+			} else
+				debug_printf(LOG_INFO, FNAME, "Bypassing address "
+				    "release because of -n flag");
 
 			/*
 			 * The client MUST stop using all of the addresses