I'm trying to implement the If-Unmodified-Since (IUMS) capability in Squid 2.x. When a client IUMS request comes, I raise a new request flag iums, store the iums time, and send an IMS request to the origin. When the origin response comes back, I modify the store entry memory objectâs reply status according to the IUMS time logic in both httpProcessReplyHeader() and clientHandleIMSReply(). This works either when the IUMS precondition is satisfied (then I send 200 to client, instead of 304 typically) or for the cache *hit only* when the IUMS precondition is unsatisfied (then I send 412 to client, instead of 200 typically). However, when the IUMS precondition is unsatisfied upon cache *miss*, the origin's 200 response is still being sent to client, even after I modify the store entry memory objectâs reply status to 412 in httpProcessReplyHeader(). I cannot figure out how and when the status is being restored back to 200. Iâve set gdb data-watch breakpoints over the store entry memory objectâs reply status. But then, later during the execution, gdb reports watchpoint expression error: bad address. Iâm stuck now, and would really appreciate any help. Thanks. On Tue, Jan 11, 2011 at 2:38 PM, Guy Bashkansky <guybas@xxxxxxxxx> wrote: > > I have to modify the behavior of a customized version of Squid 2.4 > STABLE6 code, either by configuration or by coding. ÂCurrently I can > not switch to any other Squid version, because of the customizations. > > > Problem description: > > - When a client sends a byte-range request with an If-Unmodified-Since > header AND the object in Squid's cache is stale, then this Squid > version generates a request to origin with both IUMS and IMS headers, > which is conflicting and undefined by RFC2616. ÂThe origin throws an > error. > > > Proposed solution: > > - On an IMS check for a content that was requested with a UIMS header, > Squid should only insert the IMS header, not the IUMS header. (If > only the IUMS header was added, then the origin would return origin > content unnecessarily, since it hasn't changed from the the cached > version.) > > - Once the origin check is complete, then Squid cache should compute > IUMS calculations as defined in RFC2616, returning possibly a 206 > Partial or 412 precondition failed. > http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html > > > Questions: > > - Is there any possibility to facilitate such behavior using Squid 2.4 > STABLE6 configuration? > > - If not, then where in the code should I start to look to make the > necessary code change, and approximately how? > > - I could not find any notion of If-Unmodified-Since in the Squid 2.4 > STABLE6 code. ÂWhat's the best way to handle this?
