ipv6: addrconf: reduce default temp_valid_lft to 2 days

This is a recommendation from RFC 8981 and it was intended to be changed
by commit 969c546 ("ipv6: Implement draft-ietf-6man-rfc4941bis")
but it only changed the sysctl documentation.

Signed-off-by: Fernando Fernandez Mancera <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: ffmancera

include/net/addrconf.h

@@ -8,7 +8,8 @@
 
 #define MIN_VALID_LIFETIME		(2*3600)	/* 2 hours */
 
-#define TEMP_VALID_LIFETIME		(7*86400)       /* 1 week */
+/* TEMP_VALID_LIFETIME default value as specified in RFC 8981 3.8 */
+#define TEMP_VALID_LIFETIME		(2*86400)       /* 2 days */
 #define TEMP_PREFERRED_LIFETIME		(86400)         /* 24 hours */
 #define REGEN_MIN_ADVANCE		(2)             /* 2 seconds */
 #define REGEN_MAX_RETRY			(3)