From: Mark Treacy <mark@aone.com.au>

Summarized by DW:  There existed bad interaction for STALE objects which come
back as not modified, and client IMS times prior to the entry's lastmod time.
In this case we send the entry's lastmod time towards the source.  Since the
client's IMS time might be less, we can't just send back the 304 NOT MODIFIED.
We must also check if the object has changed since the client IMS time.

diff --git a/src/client_side.cc b/src/client_side.cc
index ee027dc2e94402ba92789f1b9faf4dd02e87e548..4137864128127ceb3be0b0002d9388bc22b960b2 100644 (file)
--- a/src/client_side.cc
+++ b/src/client_side.cc
@@ -1,6 +1,6 @@
 
 /*
- * $Id: client_side.cc,v 1.71 1996/12/05 21:23:53 wessels Exp $
+ * $Id: client_side.cc,v 1.72 1996/12/13 21:38:33 wessels Exp $
  *
  * DEBUG: section 33    Client-side Routines
  * AUTHOR: Duane Wessels
@@ -35,6 +35,7 @@ static void clientRedirectDone _PARAMS((void *data, char *result));
 static void icpHandleIMSReply _PARAMS((int fd, StoreEntry * entry, void *data));
 static void clientLookupDstIPDone _PARAMS((int fd, const ipcache_addrs *, void *data));
 static void clientLookupSrcFQDNDone _PARAMS((int fd, const char *fqdn, void *data));
+static int clientGetsOldEntry _PARAMS((StoreEntry *new, StoreEntry *old, request_t *request));
 
 
 static void
@@ -405,6 +406,32 @@ icpProcessExpired(int fd, void *data)
     protoDispatch(fd, url, icpState->entry, icpState->request);
 }
 
+static int
+clientGetsOldEntry(StoreEntry * new_entry, StoreEntry * old_entry, request_t * request)
+{
+    /* If the reply is anything but "Not Modified" then
+     * we must forward it to the client */
+    if (new_entry->mem_obj->reply->code != 304) {
+       debug(33, 5, "clientGetsOldEntry: NO, reply=%d\n", new_entry->mem_obj->reply->code);
+       return 0;
+    }
+    /* If the client did not send IMS in the request, then it
+     * must get the old object, not this "Not Modified" reply */
+    if (!BIT_TEST(request->flags, REQ_IMS)) {
+       debug(33, 5, "clientGetsOldEntry: YES, no client IMS\n");
+       return 1;
+    }
+    /* If the client IMS time is prior to the entry LASTMOD time we
+     * need to send the old object */
+    if (modifiedSince(old_entry, request)) {
+       debug(33, 5, "clientGetsOldEntry: YES, modified since %d\n", request->ims);
+       return 1;
+    }
+    debug(33, 5, "clientGetsOldEntry: NO, new one is fine\n");
+    return 0;
+}
+
+
 
 static void
 icpHandleIMSReply(int fd, StoreEntry * entry, void *data)
@@ -435,7 +462,10 @@ icpHandleIMSReply(int fd, StoreEntry * entry, void *data)
            icpHandleIMSReply,
            (void *) icpState);
        return;
+#if OLD
     } else if (mem->reply->code == 304 && !BIT_TEST(icpState->request->flags, REQ_IMS)) {
+#endif
+    } else if (clientGetsOldEntry(entry, icpState->old_entry, icpState->request)) {
        /* We initiated the IMS request, the client is not expecting
         * 304, so put the good one back.  First, make sure the old entry
         * headers have been loaded from disk. */
@@ -484,3 +514,34 @@ icpHandleIMSReply(int fd, StoreEntry * entry, void *data)
     icpState->old_entry = NULL;        /* done with old_entry */
     icpSendMoreData(fd, icpState);     /* give data to the client */
 }
+
+int
+modifiedSince(StoreEntry *entry, request_t *request)
+{
+    int object_length;
+    MemObject *mem = entry->mem_obj;
+    debug(33, 3, "modifiedSince: '%s'\n", entry->url);
+    if (entry->lastmod < 0)
+       return 1;
+    /* Find size of the object */
+    if (mem->reply->content_length)
+       object_length = mem->reply->content_length;
+    else
+       object_length = entry->object_len - mem->reply->hdr_sz;
+    if (entry->lastmod > request->ims) {
+       debug(33, 3, "--> YES: entry newer than client\n");
+       return 1;
+    } else if (entry->lastmod < request->ims) {
+       debug(33, 3, "-->  NO: entry older than client\n");
+       return 0;
+    } else if (request->imslen < 0) {
+       debug(33, 3, "-->  NO: same LMT, no client length\n");
+       return 0;
+    } else if (request->imslen == object_length) {
+       debug(33, 3, "-->  NO: same LMT, same length\n");
+       return 0;
+    } else {
+       debug(33, 3, "--> YES: same LMT, different length\n");
+       return 1;
+    }
+}