[9front] [patch] select correct ipv6 source when using both ULA and GUA

[Arne Meyer <meyer.arne83@netcologne.de>]

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9front has no concept of ULA addresses. We are treating ULAs as GUAs which results in selecting a ULA as a source address for GUA address space. This breaks routing when using both scopes.

Greetings,
Arne

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diff e938acc8ff64a3cbbd6ef7ba88f83e3f03ede681 uncommitted
--- a/sys/src/9/ip/ipifc.c
+++ b/sys/src/9/ip/ipifc.c
@@ -70,6 +70,7 @@
 	unknownv6,		/* UGH */
 	unspecifiedv6,
 	linklocalv6,
+	ulav6,
 	globalv6,
 };
 
@@ -81,6 +82,8 @@
 	else if(islinklocal(addr) || ipcmp(addr, v6loopback) == 0 ||
 	    isv6mcast(addr) && (addr[1] & 0xF) <= Link_local_scop)
 		return linklocalv6;
+	else if(isula(addr))
+		return ulav6;
 	else
 		return globalv6;
 }
@@ -1219,7 +1222,7 @@
 }
 
 /*
- *  find "best" (global > link local > unspecified)
+ *  find "best" (global > ula > link local > unspecified)
  *  local address; address must be current.
  */
 static void
--- a/sys/src/9/ip/ipv6.h
+++ b/sys/src/9/ip/ipv6.h
@@ -16,6 +16,7 @@
  */
 #define isv6mcast(addr)	  ((addr)[0] == 0xff)
 #define islinklocal(addr) ((addr)[0] == 0xfe && ((addr)[1] & 0xc0) == 0x80)
+#define isula(addr)		  ((addr)[0] == 0xfd)
 
 #define optexsts(np)	(nhgets((np)->ploadlen) > 24)
 #define issmcast(addr)	(memcmp((addr), v6solicitednode, 13) == 0)