router: move pref64 calculations to the config stage

If pref64 is misconfigured, it'll print a LOG_WARNING message every time a RA
is generated, which seems a bit excessive.

When fixing that, I noticed that all work is done for every RA, so I ended up
moving the gist over to the config stage where it is done once.

Signed-off-by: David Härdeman <david@hardeman.nu>

3 files changed, 48 insertions, 51 deletions

diff --git a/src/config.c b/src/config.c
index e816f4b..4e1493f 100644
--- a/src/config.c
+++ b/src/config.c
@@ -1314,10 +1314,50 @@ int config_parse_interface(void *data, size_t len, const char *name, bool overwr
 		}
 	}
 
-	if ((c = tb[IFACE_ATTR_RA_PREF64]))
+	if ((c = tb[IFACE_ATTR_RA_PREF64])) {
+		struct in6_addr addr;
+
 		odhcpd_parse_addr6_prefix(blobmsg_get_string(c),
-					  &iface->pref64_addr,
-					  &iface->pref64_length);
+					  &addr, &iface->pref64_length);
+
+		iface->pref64_prefix[0] = addr.s6_addr32[0];
+		switch (iface->pref64_length) {
+		case 96:
+			iface->pref64_plc = 0;
+			iface->pref64_prefix[1] = addr.s6_addr32[1];
+			iface->pref64_prefix[2] = addr.s6_addr32[2];
+			break;
+		case 64:
+			iface->pref64_plc = 1;
+			iface->pref64_prefix[1] = addr.s6_addr32[1];
+			iface->pref64_prefix[2] = 0;
+			break;
+		case 56:
+			iface->pref64_plc = 2;
+			iface->pref64_prefix[1] = addr.s6_addr32[1] & htonl(0xffffff00);
+			iface->pref64_prefix[2] = 0;
+			break;
+		case 48:
+			iface->pref64_plc = 3;
+			iface->pref64_prefix[1] = addr.s6_addr32[1] & htonl(0xffff0000);
+			iface->pref64_prefix[2] = 0;
+			break;
+		case 40:
+			iface->pref64_plc = 4;
+			iface->pref64_prefix[1] = addr.s6_addr32[1] & htonl(0xff000000);
+			iface->pref64_prefix[2] = 0;
+			break;
+		case 32:
+			iface->pref64_plc = 5;
+			iface->pref64_prefix[1] = 0;
+			iface->pref64_prefix[2] = 0;
+			break;
+		default:
+			syslog(LOG_WARNING, "Invalid PREF64 prefix size (%d), "
+			       "ignoring ra_pref64 option!", iface->pref64_length);
+			iface->pref64_length = 0;
+		}
+	}
 
 	if ((c = tb[IFACE_ATTR_RA_PREFERENCE])) {
 		const char *prio = blobmsg_get_string(c);
diff --git a/src/odhcpd.h b/src/odhcpd.h
index 61fb64c..779f50f 100644
--- a/src/odhcpd.h
+++ b/src/odhcpd.h
@@ -330,7 +330,8 @@ struct interface {
 	bool ra_useleasetime;
 	bool ra_dns;
 	uint8_t pref64_length;
-	struct in6_addr pref64_addr;
+	uint8_t pref64_plc;
+	uint32_t pref64_prefix[3];
 	bool no_dynamic_dhcp;
 	bool have_link_local;
 	uint8_t pio_filter_length;
diff --git a/src/router.c b/src/router.c
index b630953..2443078 100644
--- a/src/router.c
+++ b/src/router.c
@@ -438,7 +438,7 @@ struct nd_opt_pref64_info {
 	uint8_t type;
 	uint8_t len;
 	uint16_t lifetime_plc;
-	uint32_t addr[3];
+	uint32_t prefix[3];
 };
 
 struct nd_opt_dnr_info {
@@ -742,59 +742,15 @@ static int send_router_advert(struct interface *iface, const struct in6_addr *fr
 	if (iface->pref64_length) {
 		/* RFC 8781 § 4.1 rounding up lifetime to multiple of 8 */
 		uint16_t pref64_lifetime = lifetime < (UINT16_MAX - 7) ? lifetime + 7 : UINT16_MAX;
-		uint8_t prefix_length_code;
-		uint32_t mask_a1, mask_a2;
-
-		switch (iface->pref64_length) {
-		case 96:
-			prefix_length_code = 0;
-			mask_a1 = 0xffffffff;
-			mask_a2 = 0xffffffff;
-			break;
-		case 64:
-			prefix_length_code = 1;
-			mask_a1 = 0xffffffff;
-			mask_a2 = 0x00000000;
-			break;
-		case 56:
-			prefix_length_code = 2;
-			mask_a1 = 0xffffff00;
-			mask_a2 = 0x00000000;
-			break;
-		case 48:
-			prefix_length_code = 3;
-			mask_a1 = 0xffff0000;
-			mask_a2 = 0x00000000;
-			break;
-		case 40:
-			prefix_length_code = 4;
-			mask_a1 = 0xff000000;
-			mask_a2 = 0x00000000;
-			break;
-		case 32:
-			prefix_length_code = 5;
-			mask_a1 = 0x00000000;
-			mask_a2 = 0x00000000;
-			break;
-		default:
-			syslog(LOG_WARNING, "Invalid PREF64 prefix size (%d), "
-					"ignoring ra_pref64 option!", iface->pref64_length);
-			goto pref64_out;
-			break;
-		}
 
 		pref64_sz = sizeof(*pref64);
 		pref64 = alloca(pref64_sz);
-		memset(pref64, 0, pref64_sz);
 		pref64->type = ND_OPT_PREF64;
 		pref64->len = 2;
 		pref64->lifetime_plc = htons((0xfff8 & pref64_lifetime) |
-						(0x7 & prefix_length_code));
-		pref64->addr[0] = iface->pref64_addr.s6_addr32[0];
-		pref64->addr[1] = iface->pref64_addr.s6_addr32[1] & htonl(mask_a1);
-		pref64->addr[2] = iface->pref64_addr.s6_addr32[2] & htonl(mask_a2);
+					        (0x7 & iface->pref64_plc));
+		memcpy(pref64->prefix, iface->pref64_prefix, sizeof(pref64->prefix));
 	}
-pref64_out:
 	iov[IOV_RA_PREF64].iov_base = (char *)pref64;
 	iov[IOV_RA_PREF64].iov_len = pref64_sz;