config: rewrite ifid handling

* remove ifid-random;
* add ifid eui-64; mode
* make default mode fall back to ifid random;
* use arc4random() to avoid lack of randomness
* adjust the manual page accordingly
* do not pretent u_int64_t actually gives us the
  highest bit as strtoll() is used in the lexer
* wrap current and random sets into a function
* shorten the current and random internals

This doesn't break backwards compatibility except
for the ifid-random; which we never used.  We are
removing it after a very brief time in the repo
to condense the ifid feature set and making its
utility automatic to support broader use cases
out of the box.

cfparse.y

@@ -115,7 +115,7 @@ void cf_init(void);
 %}
 
 %token INTERFACE IFNAME
-%token PREFIX_INTERFACE SLA_ID SLA_LEN IFID IFID_RAND RANDOM DUID_ID
+%token PREFIX_INTERFACE SLA_ID SLA_LEN IFID EUI64 RANDOM DUID_ID
 %token ID_ASSOC IA_PD IAID IA_NA
 %token ADDRESS
 %token REQUEST SEND ALLOW PREFERENCE
@@ -139,7 +139,7 @@ void cf_init(void);
 
 %union {
 	long long num;
-	char* str;
+	char *str;
 	struct cf_list *list;
 	struct dhcp6_prefix *prefix;
 	struct dhcp6_range *range;
@@ -1069,7 +1069,7 @@ ifparam:
 			struct cf_list *l;
 
 			MAKE_CFLIST(l, IFPARAM_IFID, NULL, NULL);
-			l->num = (u_int64_t)$2;
+			l->num = $2;
 			$$ = l;
 		}
 	|	IFID RANDOM EOS
@@ -1079,11 +1079,11 @@ ifparam:
 			MAKE_CFLIST(l, IFPARAM_IFID_RAND, NULL, NULL);
 			$$ = l;
 		}
-	|	IFID_RAND EOS
+	|	IFID EUI64 EOS
 		{
 			struct cf_list *l;
 
-			MAKE_CFLIST(l, IFPARAM_IFID_RAND, NULL, NULL);
+			MAKE_CFLIST(l, IFPARAM_IFID_EUI64, NULL, NULL);
 			$$ = l;
 		}
 	;

cftoken.l

@@ -252,8 +252,8 @@ ecl		\}
 <S_CNF>sla-id { DECHO; return (SLA_ID); }
 <S_CNF>sla-len { DECHO; return (SLA_LEN); }
 <S_CNF>ifid { DECHO; return (IFID); }
-<S_CNF>ifid-random { DECHO; return (IFID_RAND); }
 <S_CNF>random { DECHO; return (RANDOM); }
+<S_CNF>eui-64 { DECHO; return (EUI64); }
 
 	/* duration */
 <S_CNF>infinity { DECHO; return (INFINITY); }

config.c

@@ -141,7 +141,9 @@ static int configure_duid(char *, struct duid *);
 static int configure_addr(struct cf_list *, struct dhcp6_list *, const char *);
 static int configure_domain(struct cf_list *, struct dhcp6_list *,
     const char *);
-static int get_default_ifid(struct prefix_ifconf *);
+static int set_default_ifid(struct prefix_ifconf *);
+static int set_current_ifid(struct prefix_ifconf *, long long);
+static int set_random_ifid(struct prefix_ifconf *);
 static void clear_poolconf(struct pool_conf *);
 static struct pool_conf *create_pool(char *, struct dhcp6_range *);
 struct host_conf *find_dynamic_hostconf(struct duid *);
@@ -531,7 +533,7 @@ add_pd_pif(iapdc, cfl0, if_count)
 {
 	struct cf_list *cfl;
 	struct prefix_ifconf *pif;
-	int i, use_default_ifid = 1;
+	int ifid_done = 0;
 
 	/* duplication check */
 	for (pif = TAILQ_FIRST(&iapdc->iapd_pif_list); pif;
@@ -581,17 +583,22 @@ add_pd_pif(iapdc, cfl0, if_count)
 				goto bad;
 			}
 			break;
-		case IFPARAM_IFID_RAND:
-			for (i = 0; i < pif->ifid_len ; i++) {
-				cfl->num = cfl->num * 2 + rand() % 2;
+		case IFPARAM_IFID_EUI64:
+			if (set_default_ifid(pif)) {
+				d_printf(LOG_NOTICE, FNAME,
+				    "failed to get default IF ID for %s",
+				    pif->ifname);
+				goto bad;
 			}
-			/* FALLTHROUGH */
+			ifid_done = 1;
+			break;
+		case IFPARAM_IFID_RAND:
+			set_random_ifid(pif);
+			ifid_done = 1;
+			break;
 		case IFPARAM_IFID:
-			for (i = sizeof(pif->ifid) -1; i >= 0; i--) {
-				pif->ifid[i] = (cfl->num >> 8 *
-				    (sizeof(pif->ifid) - 1 - i)) & 0xff;
-                        }
-			use_default_ifid = 0;
+			set_current_ifid(pif, cfl->num);
+			ifid_done = 1;
 			break;
 		default:
 			d_printf(LOG_ERR, FNAME, "%s:%d internal error: "
@@ -601,11 +608,11 @@ add_pd_pif(iapdc, cfl0, if_count)
 		}
 	}
 
-	/* XXX consider a fallback to ifid-random here */
-	if (use_default_ifid && get_default_ifid(pif)) {
+	if (!ifid_done && set_default_ifid(pif)) {
 		d_printf(LOG_NOTICE, FNAME,
-		    "failed to get default IF ID for %s", pif->ifname);
-		goto bad;
+		    "failed to get default IF ID for %s, using random ID",
+		    pif->ifname);
+		set_random_ifid(pif);
 	}
 
 	TAILQ_INSERT_TAIL(&iapdc->iapd_pif_list, pif, link);
@@ -1290,7 +1297,7 @@ configure_duid(str, duid)
 
 /* we currently only construct EUI-64 based interface ID */
 static int
-get_default_ifid(pif)
+set_default_ifid(pif)
 	struct prefix_ifconf *pif;
 {
 	struct ifaddrs *ifa, *ifap;
@@ -1378,6 +1385,33 @@ get_default_ifid(pif)
 	return (-1);
 }
 
+static int
+set_current_ifid(struct prefix_ifconf *pif, long long value)
+{
+	int i;
+
+	/* similar to EUI-64 and only passed a 64 bit SIGNED integer anyway */
+	for (i = 15; i >= 8; i--) {
+		pif->ifid[i] = value & 0xff;
+		value >>= 8;
+	}
+
+	return (0);
+}
+
+static int
+set_random_ifid(struct prefix_ifconf *pif)
+{
+	int i;
+
+	/* similar to EUI-64 and only passed a 64 bit SIGNED integer anyway */
+	for (i = 15; i >= 8; i--) {
+		pif->ifid[i] = arc4random() & 0xff;
+	}
+
+	return (0);
+}
+
 void
 configure_cleanup()
 {

config.h

@@ -274,7 +274,8 @@ enum { DECL_SEND, DECL_ALLOW, DECL_INFO_ONLY, DECL_REQUEST, DECL_DUID,
        DECL_PREFIX, DECL_PREFERENCE, DECL_SCRIPT, DECL_DELAYEDKEY,
        DECL_ADDRESS,
        DECL_RANGE, DECL_ADDRESSPOOL,
-       IFPARAM_SLA_ID, IFPARAM_SLA_LEN, IFPARAM_IFID, IFPARAM_IFID_RAND,
+       IFPARAM_SLA_ID, IFPARAM_SLA_LEN,
+       IFPARAM_IFID, IFPARAM_IFID_RAND, IFPARAM_IFID_EUI64,
        DHCPOPT_RAPID_COMMIT, DHCPOPT_AUTHINFO,
        DHCPOPT_DNS, DHCPOPT_DNSNAME,
        DHCPOPT_IA_PD, DHCPOPT_IA_NA, DHCPOPT_NTP,
@@ -287,7 +288,6 @@ enum { DECL_SEND, DECL_ALLOW, DECL_INFO_ONLY, DECL_REQUEST, DECL_DUID,
        DHCPOPT_SIP, DHCPOPT_SIPNAME,
        AUTHPARAM_PROTO, AUTHPARAM_ALG, AUTHPARAM_RDM, AUTHPARAM_KEY,
        KEYPARAM_REALM, KEYPARAM_KEYID, KEYPARAM_SECRET, KEYPARAM_EXPIRE,
-       /* XXX */
        DHCPOPT_RAW };
 
 typedef enum {DHCP6_MODE_SERVER, DHCP6_MODE_CLIENT, DHCP6_MODE_RELAY }

dhcp6c.conf.5

@@ -436,26 +436,23 @@ the default value 16 will be used.
 .It Ic ifid Ar ID ;
 This statement specifies the interface identifier value.
 .Ar ID
-must be a decimal integer.
+shall be a decimal integer.
 It will be combined with the delegated prefix and the
 .Ic sla-id
 to form a complete interface address.
 If the special value
 .Ar random
-is given, the behaviour is the same as providing
-.Ic ifid-random .
-When this option is omitted, the default is to use the EUI-64 address of the
-.Ar interface .
-.It Ic ifid-random ;
-This statement instructs the client to generate a pseudo random
-interface identifier value.
-This will override the
-.Ic ifid
-statement, if present.
-The resulting value will be combined with the delegated prefix and the
-.Ic sla-id
-to form a complete interface address.
-This option is provided for syntax compatibility.
+is given, it instructs the client to generate a pseudo random value
+during configuration parsing.
+If the special value
+.Ar eui-64
+is given, only the EUI-64 address generation will be attempted which
+reflects the historic client behaviour.
+When this option is omitted,
+.Ar eui-64
+will be used, and if it fails the client will fall back to
+.Ar random
+to allow operation for interfaces without a hardware address.
 .El
 .El
 .\"