WCCP2 patch

[Steven Wilton]

We've had a couple of problems on our caches using WCCP2 + tproxy  
where the caches registered in a different order with the different  
WCCP services (traffic to the web server VS traffic from the web  
server).  This resulted in the assignment algorithm sending traffic  
coming from a particular client to one cache, and the reply traffic to  
a different cache.


My solution is to order the linked list of web caches in the WCCP2  
code to ensure that each cache will be assigned the same has map  
regardless of when the cache registers with the router.


I've attached the patch, which we're using in production.  I'll commit  
it to head shortly unless there's any objections, and I'm not sure if  
it's worth applying to 2.6/2.7/3.0.


Steven


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Index: src/wccp2.c
===
RCS file: /cvsroot/squid/squid/src/wccp2.c,v
retrieving revision 1.29
diff -u -u -r1.29 wccp2.c
--- src/wccp2.c 26 Dec 2007 23:52:02 -  1.29
+++ src/wccp2.c 25 Jan 2008 01:10:55 -
@@ -361,6 +361,7 @@
 /* END WCCP V2 */
 void wccp2_add_service_list(int service, int service_id, int service_priority,
 int service_proto, int service_flags, int ports[], int security_type, char 
*password);
+static void wccp2SortCacheList(struct wccp2_cache_list_t *head);
 
 /*
  * The functions used during startup:
@@ -1166,6 +1167,8 @@
found = 1;
num_caches = 1;
 }
+wccp2SortCacheList(router_list_ptr-cache_list_head);
+
 router_list_ptr-num_caches = htonl(num_caches);
 
 if ((found == 1)  (service_list_ptr-lowest_ip == 1)) {
@@ -1913,6 +1916,39 @@
 }
 }
 
+static void
+wccp2SortCacheList(struct wccp2_cache_list_t *head) {
+struct wccp2_cache_list_t tmp;
+struct wccp2_cache_list_t *this_item;
+struct wccp2_cache_list_t *find_item;
+struct wccp2_cache_list_t *next_lowest;
+
+/* Go through each position in the list one at a time */
+for (this_item = head; this_item-next; this_item = this_item-next) {
+   /* Find the item with the lowest IP */
+   next_lowest = this_item;
+
+   for(find_item = this_item; find_item-next; find_item = 
find_item-next) {
+   if(find_item-cache_ip.s_addr  next_lowest-cache_ip.s_addr) {
+   next_lowest = find_item;
+   }
+   }
+   /* Swap if we need to */
+   if(next_lowest != this_item) {
+   /* First make a copy of the current item */
+   memcpy(tmp, this_item, sizeof(struct wccp2_cache_list_t));
+
+   /* Next update the pointers to maintain the linked list */
+   tmp.next=next_lowest-next;
+   next_lowest-next=this_item-next;
+
+   /* Finally copy the updated items to their correct location */
+   memcpy(this_item, next_lowest, sizeof(struct wccp2_cache_list_t));
+   memcpy(next_lowest, tmp, sizeof(struct wccp2_cache_list_t));
+   }
+}
+}
+
 void
 free_wccp2_service_info(void *v)
 {

Re: WCCP2 patch

[Alex Rousskov]

On Mon, 2008-01-28 at 21:00 +0900, Steven Wilton wrote:
 We've had a couple of problems on our caches using WCCP2 + tproxy  
 where the caches registered in a different order with the different  
 WCCP services (traffic to the web server VS traffic from the web  
 server).  This resulted in the assignment algorithm sending traffic  
 coming from a particular client to one cache, and the reply traffic to  
 a different cache.
 
 My solution is to order the linked list of web caches in the WCCP2  
 code to ensure that each cache will be assigned the same has map  
 regardless of when the cache registers with the router.
 
 I've attached the patch, which we're using in production.  I'll commit  
 it to head shortly unless there's any objections, and I'm not sure if  
 it's worth applying to 2.6/2.7/3.0.

Please port and apply to Squid 3.HEAD, at least. You may want to add a
comment that wccp2SortCacheList is doing bubble sort by IP address (if
it is).

Thanks a lot,

Alex.

Re: WCCP2 patch

[Adrian Chadd]

Hm, I think its now worth creating a Wiki article covering WCCPv2
issues and which ones have been solved. This is definitely one of
those things that should be documented.



Adrian

On Mon, Jan 28, 2008, Steven Wilton wrote:
 We've had a couple of problems on our caches using WCCP2 + tproxy  
 where the caches registered in a different order with the different  
 WCCP services (traffic to the web server VS traffic from the web  
 server).  This resulted in the assignment algorithm sending traffic  
 coming from a particular client to one cache, and the reply traffic to  
 a different cache.
 
 My solution is to order the linked list of web caches in the WCCP2  
 code to ensure that each cache will be assigned the same has map  
 regardless of when the cache registers with the router.
 
 I've attached the patch, which we're using in production.  I'll commit  
 it to head shortly unless there's any objections, and I'm not sure if  
 it's worth applying to 2.6/2.7/3.0.
 
 Steven
 
 
 This message was sent using IMP, the Internet Messaging Program.
 

 Index: src/wccp2.c
 ===
 RCS file: /cvsroot/squid/squid/src/wccp2.c,v
 retrieving revision 1.29
 diff -u -u -r1.29 wccp2.c
 --- src/wccp2.c   26 Dec 2007 23:52:02 -  1.29
 +++ src/wccp2.c   25 Jan 2008 01:10:55 -
 @@ -361,6 +361,7 @@
  /* END WCCP V2 */
  void wccp2_add_service_list(int service, int service_id, int 
 service_priority,
  int service_proto, int service_flags, int ports[], int security_type, 
 char *password);
 +static void wccp2SortCacheList(struct wccp2_cache_list_t *head);
  
  /*
   * The functions used during startup:
 @@ -1166,6 +1167,8 @@
   found = 1;
   num_caches = 1;
  }
 +wccp2SortCacheList(router_list_ptr-cache_list_head);
 +
  router_list_ptr-num_caches = htonl(num_caches);
  
  if ((found == 1)  (service_list_ptr-lowest_ip == 1)) {
 @@ -1913,6 +1916,39 @@
  }
  }
  
 +static void
 +wccp2SortCacheList(struct wccp2_cache_list_t *head) {
 +struct wccp2_cache_list_t tmp;
 +struct wccp2_cache_list_t *this_item;
 +struct wccp2_cache_list_t *find_item;
 +struct wccp2_cache_list_t *next_lowest;
 +
 +/* Go through each position in the list one at a time */
 +for (this_item = head; this_item-next; this_item = this_item-next) {
 + /* Find the item with the lowest IP */
 + next_lowest = this_item;
 +
 + for(find_item = this_item; find_item-next; find_item = 
 find_item-next) {
 + if(find_item-cache_ip.s_addr  next_lowest-cache_ip.s_addr) {
 + next_lowest = find_item;
 + }
 + }
 + /* Swap if we need to */
 + if(next_lowest != this_item) {
 + /* First make a copy of the current item */
 + memcpy(tmp, this_item, sizeof(struct wccp2_cache_list_t));
 +
 + /* Next update the pointers to maintain the linked list */
 + tmp.next=next_lowest-next;
 + next_lowest-next=this_item-next;
 +
 + /* Finally copy the updated items to their correct location */
 + memcpy(this_item, next_lowest, sizeof(struct wccp2_cache_list_t));
 + memcpy(next_lowest, tmp, sizeof(struct wccp2_cache_list_t));
 + }
 +}
 +}
 +
  void
  free_wccp2_service_info(void *v)
  {


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