The current path_calc_hash() has at least two issues and this tries to fix
them.

1. The others attributes are not included into the hash, so paths with
same main attributes but different additional attributes hash into the
same value.

2. The hash calculation covers bits it should not. Especially the
inclusion of aspa_generation is worrisome since path_equal() explicitly
excludes it.

Since siphash really prefers to operate on 64bit values reshuffle the hash
calculation to follow this as much as possible.
-- 
:wq Claudio

Index: rde.h
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/rde.h,v
diff -u -p -r1.346 rde.h
--- rde.h	30 Apr 2026 15:51:07 -0000	1.346
+++ rde.h	6 May 2026 19:22:59 -0000
@@ -227,18 +227,17 @@ struct rde_aspath {
 	struct rde_aspa_state		 aspa_state;
 	int				 refcnt;
 	uint32_t			 flags;		/* internally used */
+#define	path_starthash	 med
 	uint32_t			 med;		/* multi exit disc */
 	uint32_t			 lpref;		/* local pref */
 	uint32_t			 weight;	/* low prio lpref */
 	uint16_t			 rtlabelid;	/* route label id */
 	uint16_t			 pftableid;	/* pf table id */
 	uint8_t				 origin;
+#define	path_endhash	 others_len
 	uint8_t				 others_len;
 	uint8_t				 aspa_generation;
 };
-#define PATH_HASHOFF		offsetof(struct rde_aspath, med)
-#define PATH_HASHSTART(x)	((const uint8_t *)x + PATH_HASHOFF)
-#define PATH_HASHSIZE		(sizeof(struct rde_aspath) - PATH_HASHOFF)
 
 enum nexthop_state {
 	NEXTHOP_LOOKUP,
Index: rde_rib.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/rde_rib.c,v
diff -u -p -r1.291 rde_rib.c
--- rde_rib.c	5 May 2026 08:26:50 -0000	1.291
+++ rde_rib.c	7 May 2026 09:35:43 -0000
@@ -610,11 +610,17 @@ static uint64_t
 path_calc_hash(const struct rde_aspath *p)
 {
 	SIPHASH_CTX ctx;
+	unsigned int l;
 
 	SipHash24_Init(&ctx, &pathkey);
-	SipHash24_Update(&ctx, PATH_HASHSTART(p), PATH_HASHSIZE);
+	for (l = 0; l < p->others_len && p->others[l] != NULL; l++)
+		SipHash24_Update(&ctx, &p->others[l]->hash,
+		    sizeof(p->others[l]->hash));
 	SipHash24_Update(&ctx, aspath_dump(p->aspath),
 	    aspath_length(p->aspath));
+	SipHash24_Update(&ctx, &p->path_starthash,
+	    (const char *)&p->path_endhash - (const char *)&p->path_starthash);
+	
 	return SipHash24_End(&ctx);
 }