From: Willy Tarreau <w@1wt.eu>
Date: Tue, 29 Nov 2022 16:36:44 +0000 (+0100)
Subject: MINOR: stick-table: change the API of the function used to calculate the shard
X-Git-Tag: v2.7.0~11
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d5cae6a0c70bb9b31c3973676eba3359f765592d;p=thirdparty%2Fhaproxy.git

MINOR: stick-table: change the API of the function used to calculate the shard

The function used to calculate the shard number currently requires a
stktable_key on input for this. Unfortunately, it happens that peers
currently miss this calculation and they do not provide stktable_key
at all, instead they're open-coding all the low-level stick-table work
(hence why it's missing). Thus we'll need to be able to calculate the
shard number in keys coming from peers as well but the current API does
not make it possible.

This commit addresses this by inverting the order where the length and
the shard number are used. Now the low-level function is independent on
stksess and stktable_key, it takes a table, pointer and length and does
all the job. The upper function takes care of the type and key to get
the its length, and is for use only from stick-table code.

This doesn't change anything except that the low-level one will be usable
from outside (hence why it's exported now).
---

diff --git a/include/haproxy/stick_table.h b/include/haproxy/stick_table.h
index e78bbd646c..196aabb35e 100644
--- a/include/haproxy/stick_table.h
+++ b/include/haproxy/stick_table.h
@@ -43,6 +43,7 @@ struct stksess *stksess_new(struct stktable *t, struct stktable_key *key);
 void stksess_setkey(struct stktable *t, struct stksess *ts, struct stktable_key *key);
 void stksess_free(struct stktable *t, struct stksess *ts);
 int stksess_kill(struct stktable *t, struct stksess *ts, int decrefcount);
+int stktable_get_key_shard(struct stktable *t, const void *key, size_t len);
 
 int stktable_init(struct stktable *t);
 int stktable_parse_type(char **args, int *idx, unsigned long *type, size_t *key_size);
diff --git a/src/stick_table.c b/src/stick_table.c
index 152abf7e22..99b1d33346 100644
--- a/src/stick_table.c
+++ b/src/stick_table.c
@@ -156,39 +156,36 @@ void stksess_setkey(struct stktable *t, struct stksess *ts, struct stktable_key
 	}
 }
 
-/*
- * Initialize or update the key hash in the sticky session <ts> present in table <t>
- * from the value present in <key>.
+/* return a shard number for key <key> of len <len> present in table <t>. This
+ * takes into account the presence or absence of a peers section with shards
+ * and the number of shards, the table's hash_seed, and of course the key. The
+ * caller must pass a valid <key> and <len>. The shard number to be used by the
+ * entry is returned (from 1 to nb_shards, otherwise 0 for none).
  */
-static unsigned long long stksess_getkey_hash(struct stktable *t,
-                                              struct stksess *ts,
-                                              struct stktable_key *key)
+int stktable_get_key_shard(struct stktable *t, const void *key, size_t len)
 {
-	size_t keylen;
-
-	if (t->type == SMP_T_STR)
-		keylen = key->key_len;
-	else
-		keylen = t->key_size;
+	/* no peers section or no shards in the peers section */
+	if (!t->peers.p || !t->peers.p->nb_shards)
+		return 0;
 
-	return XXH64(key->key, keylen, t->hash_seed);
+	return XXH64(key, len, t->hash_seed) % t->peers.p->nb_shards + 1;
 }
 
 /*
  * Set the shard for <key> key of <ts> sticky session attached to <t> stick table.
- * Do nothing for stick-table without peers synchronisation.
+ * Use zero for stick-table without peers synchronisation.
  */
 static void stksess_setkey_shard(struct stktable *t, struct stksess *ts,
                                  struct stktable_key *key)
 {
-	if (!t->peers.p)
-		/* This stick-table is not attached to any peers section */
-		return;
+	size_t keylen;
 
-	if (!t->peers.p->nb_shards)
-		ts->shard = 0;
+	if (t->type == SMP_T_STR)
+		keylen = key->key_len;
 	else
-		ts->shard = stksess_getkey_hash(t, ts, key) % t->peers.p->nb_shards + 1;
+		keylen = t->key_size;
+
+	ts->shard = stktable_get_key_shard(t, key->key, keylen);
 }
 
 /*