From: Willy Tarreau <w@1wt.eu>
Date: Tue, 20 Jan 2015 18:44:50 +0000 (+0100)
Subject: MEDIUM: backend: add the crc32 hash algorithm for load balancing
X-Git-Tag: v1.6-dev1~179
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=324f07f6dddcf39d81bbb4e2f5c8445251dc8a95;p=thirdparty%2Fhaproxy.git

MEDIUM: backend: add the crc32 hash algorithm for load balancing

Since we have it available, let's make it usable for load balancing,
it comes at no cost except 3 lines of documentation.
---

diff --git a/doc/configuration.txt b/doc/configuration.txt
index 13f1f724f9..cd01724759 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -2794,6 +2794,11 @@ hash-type <method> <function> <modifier>
               data such as a source IP address or a visitor identifier in a URL
               parameter.
 
+       crc32  this is the most common CRC32 implementation as used in Ethernet,
+              gzip, PNG, etc. It is slower than the other ones but may provide
+              a better distribution or less predictable results especially when
+              used on strings.
+
     <modifier> indicates an optional method applied after hashing the key :
 
        avalanche   This directive indicates that the result from the hash
diff --git a/include/types/backend.h b/include/types/backend.h
index 6325be2bf4..446ac2af13 100644
--- a/include/types/backend.h
+++ b/include/types/backend.h
@@ -115,6 +115,7 @@
 #define BE_LB_HFCN_SDBM   0x000000 /* sdbm hash */
 #define BE_LB_HFCN_DJB2   0x400000 /* djb2 hash */
 #define BE_LB_HFCN_WT6    0x800000 /* wt6 hash */
+#define BE_LB_HFCN_CRC32  0xC00000 /* crc32 hash */
 #define BE_LB_HASH_FUNC   0xC00000 /* get/clear hash function */
 
 
diff --git a/src/backend.c b/src/backend.c
index 35edf75041..721c12ad83 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -75,6 +75,9 @@ static unsigned int gen_hash(const struct proxy* px, const char* key, unsigned l
 	case BE_LB_HFCN_WT6:
 		hash = hash_wt6(key, len);
 		break;
+	case BE_LB_HFCN_CRC32:
+		hash = hash_crc32(key, len);
+		break;
 	case BE_LB_HFCN_SDBM:
 		/* this is the default hash function */
 	default:
diff --git a/src/cfgparse.c b/src/cfgparse.c
index fe5d24ae2f..8a5dfe505f 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -4835,11 +4835,15 @@ stats_error_parsing:
 			}
 			else if (!strcmp(args[2], "djb2")) {
 				curproxy->lbprm.algo |= BE_LB_HFCN_DJB2;
-			} else if (!strcmp(args[2], "wt6")) {
+			}
+			else if (!strcmp(args[2], "wt6")) {
 				curproxy->lbprm.algo |= BE_LB_HFCN_WT6;
 			}
+			else if (!strcmp(args[2], "crc32")) {
+				curproxy->lbprm.algo |= BE_LB_HFCN_CRC32;
+			}
 			else {
-				Alert("parsing [%s:%d] : '%s' only supports 'sdbm', 'djb2' or 'wt6' hash functions.\n", file, linenum, args[0]);
+				Alert("parsing [%s:%d] : '%s' only supports 'sdbm', 'djb2', 'crc32', or 'wt6' hash functions.\n", file, linenum, args[0]);
 				err_code |= ERR_ALERT | ERR_FATAL;
 				goto out;
 			}