[DCCP]: Implement both feature-local and feature-remote Sequence Window feature
This adds full support for both local/remote Sequence Window feature, from which the
* sequence-number-validity (W) and
* acknowledgment-number-validity (W') windows
derive as specified in RFC 4340, 7.5.3.
Specifically, the following changes are introduced:
* integrated new socket fields into dccp_sk;
* updated the update_gsr/gss routines with regard to these fields, using modulo-48 arithmetic;
* updated handler code: the Sequence Window feature is located at the TX side, so the local feature is
meant if the handler-rx flag is false;
* the initialisation of `rcv_wnd' in reqsk is removed, since
(i) rcv_wnd is not used by the code anywhere;
(ii) sequence number checks are not done in the LISTEN state (table in 7.5.3);
(iii) dccp_check_req already performs more stringent checks on the Ack number validity.
Until the handshake completes with activating negotiated values, the Sequence-Window default values
(100) are used. As indicated by the comment, I think that this is more than enough. Further, it only
applies to the client, since:
* client's AWL is set in dccp_connect_init(),
* client's SWL is set in dccp_rcv_request_sent_state_process() (from the ISR of the Response),
* server's AWL/SWL are set when the new child socket is created in dccp_create_openreq_child();
but at this stage dccp_feat_activate_values() has already updated the local/remote Sequence
Window feature of the server, so it is using the latest values,
* dccp_check_req() (used on reqsk's) does not need AWL/SWL and performs more stringent checks.
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
Documentation/networking/dccp.txt | 3 ++-
include/linux/dccp.h | 6 ++++--
net/dccp/dccp.h | 16 +++++++---------
net/dccp/feat.c | 13 +++++++++++++
net/dccp/minisocks.c | 12 ++++--------
5 files changed, 30 insertions(+), 20 deletions(-)
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -1082,6 +1082,19 @@ int dccp_feat_init(struct sock *sk)
rc = dccp_feat_register_sp(fn, sp[i].feat_num, sp[i].is_local,
sp[i].mandatory, sp[i].val, sp[i].len);
+ /*
+ * Initial values for the remote and local Sequence Window feature. This
+ * is only for the client startup phase, to seed AWL/SWL. Until then,
+ * - the default of 100 is enough for 75 Request-retransmissions,
+ * - sequence window checks are not performed in state LISTEN/REQUEST,
+ * - the only Ack window check is for the Ack completing the handshake.
+ * After the handshake, local/remote Sequence Window will be updated
+ * with the negotiated values (or the defaults again if not different).
+ * The server's AWL/SWL derive directly from the negotiated values.
+ */
+ for (i = 0; rc == 0 && i <= 1; i++)
+ rc = dccp_feat_activate(sk, DCCPF_SEQUENCE_WINDOW, i, NULL);
+
kfree(sp[0].val);
kfree(sp[1].val);
return rc;
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -380,12 +380,10 @@ static inline unsigned int dccp_hdr_len(
*
* Will be used to pass the state from dccp_request_sock to dccp_sock.
*
- * @dccpms_sequence_window - Sequence Window Feature (section 7.5.2)
* @dccpms_send_ndp_count - Send NDP Count Feature (7.7.2)
* @dccpms_ack_ratio - Ack Ratio Feature (section 11.3)
*/
struct dccp_minisock {
- __u64 dccpms_sequence_window;
__u8 dccpms_send_ndp_count;
__u8 dccpms_ack_ratio;
};
@@ -486,6 +484,8 @@ struct dccp_ackvec;
* @dccps_tstamp - most recently received timestamp to echo (RFC 4340, 13.1)
* @dccps_l_ack_ratio - feature-local Ack Ratio
* @dccps_r_ack_ratio - feature-remote Ack Ratio
+ * @dccps_l_seq_win - local Sequence Window (influences ack number validity)
+ * @dccps_r_seq_win - remote Sequence Window (influences seq number validity)
* @dccps_pcslen - sender partial checksum coverage (via sockopt)
* @dccps_pcrlen - receiver partial checksum coverage (via sockopt)
* @dccps_ndp_count - number of Non Data Packets since last data packet
@@ -523,6 +523,8 @@ struct dccp_sock {
struct dccp_ts_echo *dccps_tstamp;
__u16 dccps_l_ack_ratio;
__u16 dccps_r_ack_ratio;
+ __u64 dccps_l_seq_win:48;
+ __u64 dccps_r_seq_win:48;
__u8 dccps_pcslen:4;
__u8 dccps_pcrlen:4;
unsigned long dccps_ndp_count;
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -390,23 +390,21 @@ static inline void dccp_hdr_set_ack(stru
static inline void dccp_update_gsr(struct sock *sk, u64 seq)
{
struct dccp_sock *dp = dccp_sk(sk);
- const struct dccp_minisock *dmsk = dccp_msk(sk);
dp->dccps_gsr = seq;
- dccp_set_seqno(&dp->dccps_swl,
- dp->dccps_gsr + 1 - (dmsk->dccpms_sequence_window / 4));
- dccp_set_seqno(&dp->dccps_swh,
- dp->dccps_gsr + (3 * dmsk->dccpms_sequence_window) / 4);
+ /* Sequence validity window depends on remote Sequence Window (7.5.1) */
+ dp->dccps_swl = SUB48(ADD48(dp->dccps_gsr, 1), dp->dccps_r_seq_win / 4);
+ dp->dccps_swh = ADD48(dp->dccps_gsr, (3 * dp->dccps_r_seq_win) / 4);
}
static inline void dccp_update_gss(struct sock *sk, u64 seq)
{
struct dccp_sock *dp = dccp_sk(sk);
- dp->dccps_awh = dp->dccps_gss = seq;
- dccp_set_seqno(&dp->dccps_awl,
- (dp->dccps_gss -
- dccp_msk(sk)->dccpms_sequence_window + 1));
+ dp->dccps_gss = seq;
+ /* Ack validity window depends on local Sequence Window value (7.5.1) */
+ dp->dccps_awl = SUB48(ADD48(dp->dccps_gss, 1), dp->dccps_l_seq_win);
+ dp->dccps_awh = dp->dccps_gss;
}
static inline int dccp_ack_pending(const struct sock *sk)
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -44,7 +44,6 @@ EXPORT_SYMBOL_GPL(dccp_death_row);
void dccp_minisock_init(struct dccp_minisock *dmsk)
{
- dmsk->dccpms_sequence_window = sysctl_dccp_feat_sequence_window;
dmsk->dccpms_ack_ratio = sysctl_dccp_feat_ack_ratio;
}
@@ -111,7 +110,6 @@ struct sock *dccp_create_openreq_child(s
struct dccp_request_sock *dreq = dccp_rsk(req);
struct inet_connection_sock *newicsk = inet_csk(newsk);
struct dccp_sock *newdp = dccp_sk(newsk);
- struct dccp_minisock *newdmsk = dccp_msk(newsk);
newdp->dccps_role = DCCP_ROLE_SERVER;
newdp->dccps_hc_rx_ackvec = NULL;
@@ -129,9 +127,6 @@ struct sock *dccp_create_openreq_child(s
* Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
*/
- /* See dccp_v4_conn_request */
- newdmsk->dccpms_sequence_window = req->rcv_wnd;
-
newdp->dccps_gar = newdp->dccps_isr = dreq->dreq_isr;
dccp_update_gsr(newsk, dreq->dreq_isr);
@@ -289,7 +284,6 @@ int dccp_reqsk_init(struct request_sock
inet_rsk(req)->rmt_port = dccp_hdr(skb)->dccph_sport;
inet_rsk(req)->acked = 0;
- req->rcv_wnd = sysctl_dccp_feat_sequence_window;
dreq->dreq_tstamp = NULL;
/* inherit feature negotiation options from listening socket */
@@ -325,8 +319,10 @@ int dccp_hdlr_ccid(struct sock *sk, u64
int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
{
- if (!rx)
- dccp_msk(sk)->dccpms_sequence_window = seq_win;
+ if (rx)
+ dccp_sk(sk)->dccps_r_seq_win = seq_win;
+ else
+ dccp_sk(sk)->dccps_l_seq_win = seq_win;
return 0;
}
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -147,7 +147,8 @@ ack_ratio = 2
The default Ack Ratio (sec. 11.3) to use.
seq_window = 100
- The initial sequence window (sec. 7.5.2).
+ The initial sequence window (sec. 7.5.2) of the sender. This influences
+ the local ackno validity and the remote seqno validity windows (7.5.1).
tx_qlen = 5
The size of the transmit buffer in packets. A value of 0 corresponds
-
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