This provides a routine to consistently update the buffer state when the
peer acknowledges receipt of Ack Vectors; updating state in the list of Ack
Vectors as well as in the circular buffer.
While based on RFC 4340, several additional (and necessary) precautions were
added to protect the consistency of the buffer state. These additions are
essential, since analysis and experience showed that the basic algorithm was
insufficient for this task (which lead to problems that were hard to debug).
The algorithm now
* deals with HC-sender acknowledging to HC-receiver and vice versa,
* keeps track of the last unacknowledged but received seqno in tail_ackno,
* has special cases to reset the overflow condition when appropriate,
* is protected against receiving older information (would mess up buffer state).
Note: The older code performed an unnecessary step, where the sender cleared
Ack Vector state by parsing the Ack Vector received by the HC-receiver. Doing
this was entirely redundant, since
* the receiver always puts the full acknowledgment window (groups 2,3 in 11.4.2)
into the Ack Vectors it sends; hence the HC-receiver is only interested in the
highest state that the HC-sender received;
* this means that the acknowledgment number on the (Data)Ack from the HC-sender
is sufficient; and work done in parsing earlier state is not necessary, since
the later state subsumes the earlier one (see also RFC 4340, A.4).
This older interface (dccp_ackvec_parse()) is therefore removed.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This patch brings the Ack Vector interface up to date. Its main purpose is
to lay the basis for the subsequent patches of this set, which will use the
new data structure fields and routines.
There are no real algorithmic changes, rather an adaptation:
(1) Replaced the static Ack Vector size (2) with a #define so that it can
be adapted (with low loss / Ack Ratio, a value of 1 works, so 2 seems
to be sufficient for the moment) and added a solution so that computing
the ECN nonce will continue to work - even with larger Ack Vectors.
(2) Replaced the #defines for Ack Vector states with a complete enum.
(3) Replaced #defines to compute Ack Vector length and state with general
purpose routines (inlines), and updated code to use these.
(4) Added a `tail' field (conversion to circular buffer in subsequent patch).
(5) Updated the (outdated) documentation for Ack Vector struct.
(6) All sequence number containers now trimmed to 48 bits.
(7) Removal of unused bits:
* removed dccpav_ack_nonce from struct dccp_ackvec, since this is already
redundantly stored in the `dccpavr_ack_nonce' (of Ack Vector record);
* removed Elapsed Time for Ack Vectors (it was nowhere used);
* replaced semantics of dccpavr_sent_len with dccpavr_ack_runlen, since
the code needs to be able to remember the old run length;
* reduced the de-/allocation routines (redundant / duplicate tests).
Justification for removing Elapsed Time information [can be removed]:
---------------------------------------------------------------------
1. The Elapsed Time information for Ack Vectors was nowhere used in the code.
2. DCCP does not implement rate-based pacing of acknowledgments. The only
recommendation for always including Elapsed Time is in section 11.3 of
RFC 4340: "Receivers that rate-pace acknowledgements SHOULD [...]
include Elapsed Time options". But such is not the case here.
3. It does not really improve estimation accuracy. The Elapsed Time field only
records the time between the arrival of the last acknowledgeable packet and
the time the Ack Vector is sent out. Since Linux does not (yet) implement
delayed Acks, the time difference will typically be small, since often the
arrival of a data packet triggers sending feedback at the HC-receiver.
Justification for changes in de-/allocation routines [can be removed]:
----------------------------------------------------------------------
* INIT_LIST_HEAD in dccp_ackvec_record_new was redundant, since the list
pointers were later overwritten when the node was added via list_add();
* dccp_ackvec_record_new() was called in a single place only;
* calls to list_del_init() before calling dccp_ackvec_record_delete() were
redundant, since subsequently the entire element was k-freed;
* since all calls to dccp_ackvec_record_delete() were preceded to a call to
list_del_init(), the WARN_ON test would never evaluate to true;
* since all calls to dccp_ackvec_record_delete() were made from within
list_for_each_entry_safe(), the test for avr == NULL was redundant;
* list_empty() in ackvec_free was redundant, since the same condition is
embedded in the loop condition of the subsequent list_for_each_entry_safe().
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This fixes a problem and a potential loophole with regard to seqno/ackno
validity: the problem is that the initial adjustments to AWL/SWL were
only performed at the begin of the connection, during the handshake.
Since the Sequence Window feature is always greater than Wmin=32 (7.5.2),
it is however necessary to perform these adjustments at least for the first
W/W' (variables as per 7.5.1) packets in the lifetime of a connection.
This requirement is complicated by the fact that W/W' can change at any time
during the lifetime of a connection.
Therefore the consequence is to perform this safety check each time SWL/AWL
are updated.
A second problem solved by this patch is that the remote/local Sequence Window
feature values (which set the bounds for AWL/SWL/SWH) are undefined until the
feature negotiation has completed.
During the initial handshake we have more stringent sequence number protection,
the changes added by this patch effect that {A,S}W{L,H} are within the correct
bounds at the instant that feature negotiation completes (since the SeqWin
feature activation handlers call dccp_update_gsr/gss()).
A detailed rationale is below -- can be removed from the commit message.
1. Server sequence number checks during initial handshake
---------------------------------------------------------
The server can not use the fields of the listening socket for seqno/ackno checks
and thus needs to store all relevant information on a per-connection basis on
the dccp_request socket. This is a size-constrained structure and has currently
only ISS (dreq_iss) and ISR (dreq_isr) defined.
Adding further fields (SW{L,H}, AW{L,H}) would increase the size of the struct
and it is questionable whether this will have any practical gain. The currently
implemented solution is as follows.
* receiving first Request: dccp_v{4,6}_conn_request sets
ISR := P.seqno, ISS := dccp_v{4,6}_init_sequence()
* sending first Response: dccp_v{4,6}_send_response via dccp_make_response()
sets P.seqno := ISS, sets P.ackno := ISR
* receiving retransmitted Request: dccp_check_req() overrides ISR := P.seqno
* answering retransmitted Request: dccp_make_response() sets ISS += 1,
otherwise as per first Response
* completing the handshake: succeeds in dccp_check_req() for the first Ack
where P.ackno == ISS (P.seqno is not tested)
* creating child socket: ISS, ISR are copied from the request_sock
This solution will succeed whenever the server can receive the Request and the
subsequent Ack in succession, without retransmissions. If there is packet loss,
the client needs to retransmit until this condition succeeds; it will otherwise
eventually give up. Adding further fields to the request_sock could increase
the robustness a bit, in that it would make possible to let a reordered Ack
(from a retransmitted Response) pass. The argument against such a solution is
that if the packet loss is not persistent and an Ack gets through, why not
wait for the one answering the original response: if the loss is persistent, it
is probably better to not start the connection in the first place.
Long story short: the present design (by Arnaldo) is simple and will likely work
just as well as a more complicated solution. As a consequence, {A,S}W{L,H} are
not needed until the moment the request_sock is cloned into the accept queue.
At that stage feature negotiation has completed, so that the values for the local
and remote Sequence Window feature (7.5.2) are known, i.e. we are now in a better
position to compute {A,S}W{L,H}.
2. Client sequence number checks during initial handshake
---------------------------------------------------------
Until entering PARTOPEN the client does not need the adjustments, since it
constrains the Ack window to the packet it sent.
* sending first Request: dccp_v{4,6}_connect() choose ISS,
dccp_connect() then sets GAR := ISS (as per 8.5),
dccp_transmit_skb() (with the previous bug fix) sets
GSS := ISS, AWL := ISS, AWH := GSS
* n-th retransmitted Request (with previous patch):
dccp_retransmit_skb() via timer calls
dccp_transmit_skb(), which sets GSS := ISS+n
and then AWL := ISS, AWH := ISS+n
* receiving any Response: dccp_rcv_request_sent_state_process()
-- accepts packet if AWL <= P.ackno <= AWH;
-- sets GSR = ISR = P.seqno
* sending the Ack completing the handshake: dccp_send_ack() calls
dccp_transmit_skb(), which sets GSS += 1
and AWL := ISS, AWH := GSS
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This removes the use of the sysctl and the minisock variable for the Send Ack
Vector feature, which is now handled fully dynamically via feature negotiation;
i.e. when CCID2 is enabled, Ack Vectors are automatically enabled (as per
RFC 4341, 4.).
Using a sysctl in parallel to this implementation would open the door to
crashes, since much of the code relies on tests of the boolean minisock /
sysctl variable. Thus, this patch replaces all tests of type
if (dccp_msk(sk)->dccpms_send_ack_vector)
/* ... */
with
if (dp->dccps_hc_rx_ackvec != NULL)
/* ... */
The dccps_hc_rx_ackvec is allocated by the dccp_hdlr_ackvec() when feature
negotiation concluded that Ack Vectors are to be used on the half-connection.
Otherwise, it is NULL (due to dccp_init_sock/dccp_create_openreq_child),
so that the test is a valid one.
The activation handler for Ack Vectors is called as soon as the feature
negotiation has concluded at the
* server when the Ack marking the transition RESPOND => OPEN arrives;
* client after it has sent its ACK, marking the transition REQUEST => PARTOPEN.
Adding the sequence number of the Response packet to the Ack Vector has been
removed, since
(a) connection establishment implies that the Response has been received;
(b) the CCIDs only look at packets received in the (PART)OPEN state, i.e.
this entry will always be ignored;
(c) it can not be used for anything useful - to detect loss for instance, only
packets received after the loss can serve as pseudo-dupacks.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
This integrates feature-activation in the client, with these details:
1. When dccp_parse_options() fails, the reset code is already set, request_sent
_state_process() currently overrides this with `Packet Error', which is not
intended - so changed to use the reset code set in dccp_parse_options();
2. There was a FIXME to change the error code when dccp_ackvec_add() fails.
I have looked this up and found that:
* the check whether ackno < ISN is already made earlier,
* this Response is likely the 1st packet with an Ackno that the client gets,
* so when dccp_ackvec_add() fails, the reason is likely not a packet error.
3. When feature negotiation fails, the socket should be marked as not usable,
so that the application is notified that an error occurs. This is achieved
by a new label, which uses an error code of `Aborted' and which sets the
socket state to CLOSED, as well as sk_err.
4. Avoids parsing the Ack twice in Respond state by not doing option processing
again in dccp_rcv_respond_partopen_state_process (as option processing has
already been done on the request_sock in dccp_check_req).
Since this addresses congestion-control initialisation, a corresponding
FIXME has been removed.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
This provides feature-negotiation initialisation for both DCCP sockets and
DCCP request_sockets, to support feature negotiation during connection setup.
It also resolves a FIXME regarding the congestion control initialisation.
Thanks to Wei Yongjun for help with the IPv6 side of this patch.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
RFC4340 states that if a packet is received with an option error (such as a
Mandatory Option as the last byte of the option list), the endpoint should
repond with a Reset.
In the LISTEN and RESPOND states, the endpoint correctly reponds with Reset,
while in the REQUEST/OPEN states, packets with option errors are just ignored.
The packet sequence is as follows:
Case 1:
Endpoint A Endpoint B
(CLOSED) (CLOSED)
<---------------- REQUEST
RESPONSE -----------------> (*1)
(with invalid option)
<---------------- RESET
(with Reset Code 5, "Option Error")
(*1) currently just ignored, no Reset is sent
Case 2:
Endpoint A Endpoint B
(OPEN) (OPEN)
DATA-ACK -----------------> (*2)
(with invalid option)
<---------------- RESET
(with Reset Code 5, "Option Error")
(*2) currently just ignored, no Reset is sent
This patch fixes the problem, by generating a Reset instead of silently
ignoring option errors.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Thanks is due to Wei Yongjun for the detailed analysis and description of this
bug at http://marc.info/?l=dccp&m=121739364909199&w=2
The problem is that invalid packets received by a client in state REQUEST cause
the retransmission timer for the DCCP-Request to be reset. This includes freeing
the Request-skb ( in dccp_rcv_request_sent_state_process() ). As a consequence,
* the arrival of further packets cause a double-free, triggering a panic(),
* the connection then may hang, since further retransmissions are blocked.
This patch changes the order of statements so that the retransmission timer is
reset, and the pending Request freed, only if a valid Response has arrived (or
the number of sysctl-retries has been exhausted).
Further changes:
----------------
To be on the safe side, replaced __kfree_skb with kfree_skb so that if due to
unexpected circumstances the sk_send_head is NULL the WARN_ON is used instead.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Removes legacy reinvent-the-wheel type thing. The generic
machinery integrates much better to automated debugging aids
such as kerneloops.org (and others), and is unambiguous due to
better naming. Non-intuively BUG_TRAP() is actually equal to
WARN_ON() rather than BUG_ON() though some might actually be
promoted to BUG_ON() but I left that to future.
I could make at least one BUILD_BUG_ON conversion.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
The option parsing code currently only parses on full sk's. This causes a problem for
options sent during the initial handshake (in particular timestamps and feature-negotiation
options). Therefore, this patch extends the option parsing code with an additional argument
for request_socks: if it is non-NULL, options are parsed on the request socket, otherwise
the normal path (parsing on the sk) is used.
Subsequent patches, which implement feature negotiation during connection setup, make use
of this facility.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch performs two changes:
1) Close the write-end in addition to the read-end when a fin-like segment
(Close or CloseReq) is received by DCCP. This accounts for the fact that DCCP,
in contrast to TCP, does not have a half-close. RFC 4340 says in this respect
that when a fin-like segment has been sent there is no guarantee at all that
any further data will be processed.
Thus this patch performs SHUT_WR in addition to the SHUT_RD when a fin-like
segment is encountered.
2) Minor change: I noted that code appears twice in different places and think it
makes sense to put this into a self-contained function (dccp_enqueue()).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This removes a redundant test for unexpected packet types. In dccp_rcv_state_process
it is tested twice whether a DCCP-server has received a CloseReq (Step 7):
* first in the combined if-statement,
* then in the call to dccp_rcv_closereq().
The latter is necesssary since dccp_rcv_closereq() is also called from
__dccp_rcv_established().
This patch removes the duplicate test.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This adds the necessary state transitions for the two forms of passive-close
* PASSIVE_CLOSE - which is entered when a host receives a Close;
* PASSIVE_CLOSEREQ - which is entered when a client receives a CloseReq.
Here is a detailed account of what the patch does in each state.
1) Receiving CloseReq
The pseudo-code in 8.5 says:
Step 13: Process CloseReq
If P.type == CloseReq and S.state < CLOSEREQ,
Generate Close
S.state := CLOSING
Set CLOSING timer.
This means we need to address what to do in CLOSED, LISTEN, REQUEST, RESPOND, PARTOPEN, and OPEN.
* CLOSED: silently ignore - it may be a late or duplicate CloseReq;
* LISTEN/RESPOND: will not appear, since Step 7 is performed first (we know we are the client);
* REQUEST: perform Step 13 directly (no need to enqueue packet);
* OPEN/PARTOPEN: enter PASSIVE_CLOSEREQ so that the application has a chance to process unread data.
When already in PASSIVE_CLOSEREQ, no second CloseReq is enqueued. In any other state, the CloseReq is ignored.
I think that this offers some robustness against rare and pathological cases: e.g. a simultaneous close where
the client sends a Close and the server a CloseReq. The client will then be retransmitting its Close until it
gets the Reset, so ignoring the CloseReq while in state CLOSING is sane.
2) Receiving Close
The code below from 8.5 is unconditional.
Step 14: Process Close
If P.type == Close,
Generate Reset(Closed)
Tear down connection
Drop packet and return
Thus we need to consider all states:
* CLOSED: silently ignore, since this can happen when a retransmitted or late Close arrives;
* LISTEN: dccp_rcv_state_process() will generate a Reset ("No Connection");
* REQUEST: perform Step 14 directly (no need to enqueue packet);
* RESPOND: dccp_check_req() will generate a Reset ("Packet Error") -- left it at that;
* OPEN/PARTOPEN: enter PASSIVE_CLOSE so that application has a chance to process unread data;
* CLOSEREQ: server performed active-close -- perform Step 14;
* CLOSING: simultaneous-close: use a tie-breaker to avoid message ping-pong (see comment);
* PASSIVE_CLOSEREQ: ignore - the peer has a bug (sending first a CloseReq and now a Close);
* TIMEWAIT: packet is ignored.
Note that the condition of receiving a packet in state CLOSED here is different from the condition "there
is no socket for such a connection": the socket still exists, but its state indicates it is unusable.
Last, dccp_finish_passive_close sets either DCCP_CLOSED or DCCP_CLOSING = TCP_CLOSING, so that
sk_stream_wait_close() will wait for the final Reset (which will trigger CLOSING => CLOSED).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The sock_wake_async() performs a bit different actions
depending on "how" argument. Unfortunately this argument
ony has numerical magic values.
I propose to give names to their constants to help people
reading this function callers understand what's going on
without looking into this function all the time.
I suppose this is 2.6.25 material, but if it's not (or the
naming seems poor/bad/awful), I can rework it against the
current net-2.6 tree.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This extends the DCCP socket API by honouring any shutdown(2) option set by the user.
The behaviour is, as much as possible, made consistent with the API for TCP's shutdown.
This patch exploits the information provided by the user via the socket API to reduce
processing costs:
* if the read end is closed (SHUT_RD), it is not necessary to deliver to input CCID;
* if the write end is closed (SHUT_WR), the same idea applies, but with a difference -
as long as the TX queue has not been drained, we need to receive feedback to keep
congestion-control rates up to date. Hence SHUT_WR is honoured only after the last
packet (under congestion control) has been sent;
* although SHUT_RDWR seems nonsensical, it is nevertheless supported in the same manner
as for TCP (and agrees with test for SHUTDOWN_MASK in dccp_poll() in net/dccp/proto.c).
Furthermore, most of the code already honours the sk_shutdown flags (dccp_recvmsg() for
instance sets the read length to 0 if SHUT_RD had been called); CCID handling is now added
to this by the present patch.
There will also no longer be any delivery when the socket is in the final stages, i.e. when
one of dccp_close(), dccp_fin(), or dccp_done() has been called - which is fine since at
that stage the connection is its final stages.
Motivation and background are on http://www.erg.abdn.ac.uk/users/gerrit/dccp/notes/shutdown
A FIXME has been added to notify the other end if SHUT_RD has been set (RFC 4340, 11.7).
Note: There is a comment in inet_shutdown() in net/ipv4/af_inet.c which asks to "make
sure the socket is a TCP socket". This should probably be extended to mean
`TCP or DCCP socket' (the code is also used by UDP and raw sockets).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This adds support for converting the 11 currently defined Reset codes into system
error numbers, which are stored in sk_err for further interpretation.
This makes the externally visible API behaviour similar to TCP, since a client
connecting to a non-existing port will experience ECONNREFUSED.
* Code 0, Unspecified, is interpreted as non-error (0);
* Code 1, Closed (normal termination), also maps into 0;
* Code 2, Aborted, maps into "Connection reset by peer" (ECONNRESET);
* Code 3, No Connection and
Code 7, Connection Refused, map into "Connection refused" (ECONNREFUSED);
* Code 4, Packet Error, maps into "No message of desired type" (ENOMSG);
* Code 5, Option Error, maps into "Illegal byte sequence" (EILSEQ);
* Code 6, Mandatory Error, maps into "Operation not supported on transport endpoint" (EOPNOTSUPP);
* Code 8, Bad Service Code, maps into "Invalid request code" (EBADRQC);
* Code 9, Too Busy, maps into "Too many users" (EUSERS);
* Code 10, Bad Init Cookie, maps into "Invalid request descriptor" (EBADR);
* Code 11, Aggression Penalty, maps into "Quota exceeded" (EDQUOT)
which makes sense in terms of using more than the `fair share' of bandwidth.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Do not define the sysctl_dccp_sync_ratelimit sysctl variable in the
CONFIG_SYSCTL dependent sysctl.c module - move it to input.c instead.
This fixes the following build bug:
net/built-in.o: In function `dccp_check_seqno':
input.c:(.text+0xbd859): undefined reference to `sysctl_dccp_sync_ratelimit'
distcc[29953] ERROR: compile (null) on localhost failed
make: *** [vmlinux] Error 1
Found via 'make randconfig' build testing.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This implements a SHOULD from RFC 4340, 7.5.4:
"To protect against denial-of-service attacks, DCCP implementations SHOULD
impose a rate limit on DCCP-Syncs sent in response to sequence-invalid packets,
such as not more than eight DCCP-Syncs per second."
The rate-limit is maintained on a per-socket basis. This is a more stringent
policy than enforcing the rate-limit on a per-source-address basis and
protects against attacks with forged source addresses.
Moreover, the mechanism is deliberately kept simple. In contrast to
xrlim_allow(), bursts of Sync packets in reply to sequence-invalid packets
are not supported. This foils such attacks where the receipt of a Sync
triggers further sequence-invalid packets. (I have tested this mechanism against
xrlim_allow algorithm for Syncs, permitting bursts just increases the problems.)
In order to keep flexibility, the timeout parameter can be set via sysctl; and
the whole mechanism can even be disabled (which is however not recommended).
The algorithm in this patch has been improved with regard to wrapping issues
thanks to a suggestion by Arnaldo.
Commiter note: Rate limited the step 6 DCCP_WARN too, as it says we're
sending a sync.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
This fixes the code to correspond to RFC 4340, 7.5.4, which states the
exception that a Sync received in state REQUEST generates a Reset (not
a SyncAck).
To achieve this, only a small change is required. Since
dccp_rcv_request_sent_state_process() already uses the correct Reset Code
number 4 ("Packet Error"), we only need to shift the if-statement a few
lines further down.
(To test this case: replace DCCP_PKT_RESPONSE with DCCP_PKT_SYNC
in dccp_make_response.)
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
This updates sequence number checking with regard to RFC 4340, 7.5.4.
Missing in the code was an exception for sequence-invalid Reset packets,
which get a Sync acknowledging GSR, instead of (as usual) P.seqno.
This can lead to an oscillating ping-pong flood of Reset packets.
In fact, it has been observed on the wire as follows:
1. client establishes connection to server;
2. before server can write to client, client crashes without notifying
the server (NB: now no longer possible due to ABORT function);
3. server sends DCCP-Data packet (has no ackno);
4. client generates Reset "No Connection", seqno=0, increments seqno;
5. server replies with Sync, using ackno = P.seqno;
6. client generates Reset "No Connection" with seqno = ackno + 1;
7. goto (5).
The difference is that now in (5) the server uses GSR. This causes the
Reset sent by the client in (6) to become sequence-valid, so that in (7)
the vicious circle is broken; the Reset is then enqueued and causes the
socket to enter TIMEWAIT state.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch is in part required by the next patch; it
* replaces 6 instances of `DCCP_SKB_CB(skb)->dccpd_seq' with `seqno';
* replaces 7 instances of `DCCP_SKB_CB(skb)->dccpd_ack_seq' with `ackno';
* replaces 1 use of dccp_inc_seqno() by unfolding `ADD48' macro in place.
No changes in algorithm, all changes are text replacement/substitution.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
The third parameter of dccp_sample_rtt now becomes useless and is removed.
Also combined the subtraction of the timestamp echo and the elapsed time.
This is safe, since (a) presence of timestamp echo is tested first and (b)
elapsed time is either present and non-zero or it is not set and equals 0
due to the memset in dccp_parse_options.
To avoid measuring option-processing time, the timestamp for measuring the
initial Request/Response RTT sample is taken directly when the function is
called (the Linux implementation always adds a timestamp on the Request,
so there is no loss in doing this).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
A recurring problem, in particular in the CCID code, is that RTT samples
from packets with timestamp echo and elapsed time options need to be taken.
This service is provided via a new function dccp_sample_rtt in this patch.
Furthermore, to protect against `insane' RTT samples, the sampled value
is bounded between 100 microseconds and 4 seconds - for which u32 is sufficient.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This removes two ambiguities in employing the new definition of before48,
following the analysis on http://www.mail-archive.com/dccp@vger.kernel.org/msg01295.html
(1) Updating GSR when P.seqno >= S.SWL
With the old definition we did not update when P.seqno and S.SWL are 2^47 apart. To
ensure the same behaviour as with the old definition, this is replaced with the
equivalent condition dccp_delta_seqno(S.SWL, P.seqno) >= 0
(2) Sending SYNC when P.seqno >= S.OSR
Here it is debatable whether the new definition causes an ambiguity: the case is
similar to (1); and to have consistency with the case (1), we use the equivalent
condition dccp_delta_seqno(S.OSR, P.seqno) >= 0
Detailed Justification
This reverts an earlier patch which disabled bidirectional mode, meaning that
a listening (passive) socket was not allowed to write to the other (active)
end of the connection.
This mode had been disabled when there were problems with CCID3, but it
imposes a constraint on socket programming and thus hinders deployment.
A change is included to ignore RX feedback received by the TX CCID3 module.
Many thanks to Andre Noll for pointing out this issue.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
This fixes a bug caused by a previous patch, which causes DCCP servers in
LISTEN state to not receive packets.
This patch changes the logic so that
* servers in either LISTEN or OPEN state get the RX half connection packets
* clients in OPEN state get the TX half connection packets
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
That accumulated over the last months hackaton, shame on me for not
using git-apply whitespace helping hand, will do that from now on.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This is an optimisation to reduce CPU load. The received feedback is now
only directed to the active CCID component, without requiring processing
also by the inactive one.
As a consequence, a similar test in ccid3.c is now redundant and is
also removed.
Justification:
Currently DCCP works as a unidirectional service, i.e. a listening server
is not at the same time a connecting client.
As far as I can see, several modifications are necessary until that
becomes possible.
At the present time, received feedback is both fed to the rx/tx CCID
modules. In unidirectional service, only one of these is active at any
one time.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This reaps the benefit of the earlier patch, which changed the type of
CCID 3 states to use enums, in that many conditions are now simplified
and the number of possible (unexpected) values is greatly reduced.
In a few instances, this also allowed to simplify pre-conditions; where
care has been taken to retain logical equivalence.
[DCCP]: Introduce a consistent BUG/WARN message scheme
This refines the existing set of DCCP messages so that
* BUG(), BUG_ON(), WARN_ON() have meaningful DCCP-specific counterparts
* DCCP_CRIT (for severe warnings) is not rate-limited
* DCCP_WARN() is introduced as rate-limited wrapper
Using these allows a faster and cleaner transition to their original
counterparts once the code has matured into a full DCCP implementation.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Sorts out the comments for processing steps 2,3 in section 8.5 of RFC 4340.
All comments have been updated against this document, and the reference to step
2 has been made consistent throughout the files.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Updates the references to spec documents throughout the code, taking into
account that
* the DCCP, CCID 2, and CCID 3 drafts all became RFCs in March this year
* RFC 1063 was obsoleted by RFC 1191
* draft-ietf-tcpimpl-pmtud-0x.txt was published as an Informational
RFC, RFC 2923 on 2000-09-22.
All references verified.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This will later be included in struct dccp_request_sock so that we can
have per connection feature negotiation state while in the 3way
handshake, when we clone the DCCP_ROLE_LISTEN socket (in
dccp_create_openreq_child) we'll just copy this state from
dreq_minisock to dccps_minisock.
Also the feature negotiation and option parsing code will mostly touch
dccps_minisock, which will simplify some stuff.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Renaming it to dccp_send_reset and moving it from the ipv4 specific
code to the core dccp code.
This fixes some bugs in IPV6 where timers would send v4 resets, etc.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1. No need for ->ccid_init nor ->ccid_exit, this is what module_{init,exit}
does and anynways neither ccid2 nor ccid3 were using it.
2. Rename struct ccid to struct ccid_operations and introduce struct ccid
with a pointer to ccid_operations and rigth after it the rx or tx
private state.
3. Remove the pointer to the state of the half connections from struct
dccp_sock, now its derived thru ccid_priv() from the ccid pointer.
Now we also can implement the setsockopt for changing the CCID easily as
no ccid init routines can affect struct dccp_sock in any way that prevents
other CCIDs from working if a CCID switch operation is asked by apps.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The CCID should be notified of packet reception only when a packet is
valid. Therefore, the ACK vector needs to be processed before
notifying the CCID. Also, the CCID might need information provided by
the ACK vector.
Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
If ACK vectors are used, each packet with an ACK should contain an ACK
vector. The only exception currently is response packets. It
probably is not a good idea to store ACK vector state before the
connection is completed (to help protect from syn floods).
Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When packets are received, the connection is either in DCCP_OPEN
[fast-path] or it isn't. If it's not [e.g. DCCP_PARTOPEN] upper
layers will perform sanity checks and parse options. If it is in
DCCP_OPEN, dccp_rcv_established() will do it. It is important not to
re-parse options in dccp_rcv_established() when it is not called from
the fast-path. Else, fore example, the ack vector will be added twice
and the CCID will see the packet twice.
The solution is to always enfore sanity checks from the upper layers.
When packets arrive in the fast-path, sanity checks will be performed
before calling dccp_rcv_established().
Note(acme): I rewrote the patch to achieve the same result but keeping
dccp_rcv_established with the previous semantics and having it split
into __dccp_rcv_established, that doesn't does do any sanity check,
code in state != DCCP_OPEN use this lighter version as they already do
the sanity checks.
Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
As DCCP needs to be called in the same spots.
Now we have a member in inet_sock (is_icsk), set at sock creation time from
struct inet_protosw->flags (if INET_PROTOSW_ICSK is set, like for TCP and
DCCP) to see if a struct sock instance is a inet_connection_sock for places
like the ones in ip_sockglue.c (v4 and v6) where we previously were looking if
sk_type was SOCK_STREAM, that is insufficient because we now use the same code
for DCCP, that has sk_type SOCK_DCCP.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Basically exports a similar set of functions as the one exported by
the non-AF specific TCP code.
In the process moved some non-AF specific code from dccp_v4_connect to
dccp_connect_init and moved the checksum verification from
dccp_invalid_packet to dccp_v4_rcv, so as to use it in dccp_v6_rcv
too.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
And make the core DCCP code AF agnostic, just like TCP, now its time
to work on net/dccp/ipv6.c, we are close to the end!
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Noticed by Andrea Bittau, that provided a patch that was modified to
not transition from RESPOND to OPEN when receiving DATA packets.
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Isolating it, that will be used when we introduce a CCID2 (TCP-Like)
implementation.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Moving the setting of DCCP_SKB_CB(skb)->dccpd_reset_code to the places
where events happen that trigger sending a RESET packet.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Eliciting a SYNCACK in response, we were handling SYNC packets
only in the DCCP_OPEN state, in dccp_rcv_established.
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
