[DRAFT][MERGE] Cleanup comm outgoing connections in trunk

Henrik Nordström wrote:
> tis 2010-05-18 klockan 23:34 +0000 skrev Amos Jeffries:
>
>> I've discovered the VC connections in DNS will need a re-working to handle
>> the new TCP connection setup handling. I've left that for now since it
>> appears that you are working on redesigning that area anyway. The new setup
>> routines will play VERY nicely with persistent TCP links to the
>> nameservers.
>
> I have not started on the DNS rewrite yet.
>
>> I took some extra time last night and broke the back of the selection and
>> forwarding rewrite. I'm now down to the fine detail build errors. When
>> those are done I'll push the branch to LP for you to do the DNS fixes on
>> top of.
>
> Ok.
>

Pushed to launchpad: lp:~yadi/squid/cleanup-comm

This builds, but has not yet been run tested.

What has changed:

ConnectionDetails objects have been renamed Comm::Connection and been
extended to hold the FD and Squids' socket flags.

Peer selection has been extended to do DNS lookups on the peers chosen
for forwarding to and produce a vector<> of possible connection
endpoints (squid local IP via tcp_outgoing_address or tproxy) and remote
server.

Various connection openers have been converted to use the new
ConnectStateData API and CommCalls (function based so far).

ConnectStateData has been moved into src/comm/ (not yet namespaced) and
had all its DNS lookup operations dropped. To be replaced by a looping
process of attempting to open a socket and join a link as described by
some Comm::Connection or vector<> of same.

ConnectStateData::connect() will go away and do some async work. Will
come back at some point by calling the handler with COMM_OK,
COMM_ERR_CONNECT, COMM_TIMEOUT and ptrs to the Comm::Connection or
vector (whichever were passed in).
  On COMM_OK the Comm::Connection pointer or the first entry of the
vector will be an open conn which we can now use.
  On COMM_ERR_CONNECT the vector will be empty (all tried and
discarded), the single ptr will be closed if not NULL.
  On COMM_TIMEOUT their content is as per COMM_ERR_CONNECT but the
vector may have untried paths still present but closed.

FD opening, FD problems, connection errors, timeouts, early remote
TCP_RST or NACK closure during the setup are all now wrapped out of
sight inside ConnectStateData.

The main-level component may set FD handlers as needed for read/write
and closure of the link in their connection-done handler where the FD
first becomes visible to them.

Besides the testing there is some work to:
  * make it obey squid.conf limits on retries and paths looked up.
  * make DNS TCP links ('VC') work again.
  * make the CommCalls proper AsynCalls and not function handler based.
  * make Comm::Connection ref-counted so we can have them stored
    in the peer details and further reduce the DNS steps.
  * make ICAP do DNS lookups to set its server Comm::Connection properly.
    For now it's stuck with the gethostbyname() blocking lookup.

Future work once this is stable is to:
  a) push the IDENT, NAT, EUI and TLS operations down into the Comm
layer with simple flags for other layers to turn them on/off as desired.
  b) make the general code pass Comm::Connection around so everything
like ACLs can access the client and server conn when they need to.

Amos

-- 
Please be using
   Current Stable Squid 2.7.STABLE9 or 3.1.3