[DCCP]: Handle timestamps on Request/Response exchange separately
In DCCP, timestamps can occur on packets anytime, CCID3 uses a timestamp(/echo) on the Request/Response
exchange. This patch addresses the following situation:
* timestamps are recorded on the listening socket;
* Responses are sent from dccp_request_sockets;
* suppose two connections reach the listening socket with very small time in between:
* the first timestamp value gets overwritten by the second connection request.
This is not really good, so this patch separates timestamps into
* those which are received by the server during the initial handshake (on dccp_request_sock);
* those which are received by the client or the client after connection establishment.
As before, a timestamp of 0 is regarded as indicating that no (meaningful) timestamp has been
received (in addition, a warning message is printed if hosts send 0-valued timestamps).
The timestamp-echoing now works as follows:
* when a timestamp is present on the initial Request, it is placed into dreq, due to the
call to dccp_parse_options in dccp_v{4,6}_conn_request;
* when a timestamp is present on the Ack leading from RESPOND => OPEN, it is copied over
from the request_sock into the child cocket in dccp_create_openreq_child;
* timestamps received on an (established) dccp_sock are treated as before.
Since Elapsed Time is measured in hundredths of milliseconds (13.2), the new dccp_timestamp()
function is used, as it is expected that the time between receiving the timestamp and
sending the timestamp echo will be very small against the wrap-around time. As a byproduct,
this allows smaller timestamping-time fields.
Furthermore, inserting the Timestamp Echo option has been taken out of the block starting with
'!dccp_packet_without_ack()', since Timestamp Echo can be carried on any packet (5.8 and 13.3).
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/options.c b/net/dccp/options.c
index f496d4d..0c996d8 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -166,16 +166,27 @@
case DCCPO_TIMESTAMP:
if (len != 4)
goto out_invalid_option;
-
+ /*
+ * RFC 4340 13.1: "The precise time corresponding to
+ * Timestamp Value zero is not specified". We use
+ * zero to indicate absence of a meaningful timestamp.
+ */
opt_val = get_unaligned((__be32 *)value);
- opt_recv->dccpor_timestamp = ntohl(opt_val);
+ if (unlikely(opt_val == 0)) {
+ DCCP_WARN("Timestamp with zero value\n");
+ break;
+ }
- /* FIXME: if dreq != NULL, don't store this on listening socket */
- dp->dccps_timestamp_echo = opt_recv->dccpor_timestamp;
- dp->dccps_timestamp_time = ktime_get_real();
-
+ if (dreq != NULL) {
+ dreq->dreq_timestamp_echo = ntohl(opt_val);
+ dreq->dreq_timestamp_time = dccp_timestamp();
+ } else {
+ opt_recv->dccpor_timestamp =
+ dp->dccps_timestamp_echo = ntohl(opt_val);
+ dp->dccps_timestamp_time = dccp_timestamp();
+ }
dccp_pr_debug("%s rx opt: TIMESTAMP=%u, ackno=%llu\n",
- dccp_role(sk), opt_recv->dccpor_timestamp,
+ dccp_role(sk), ntohl(opt_val),
(unsigned long long)
DCCP_SKB_CB(skb)->dccpd_ack_seq);
break;
@@ -393,16 +404,24 @@
EXPORT_SYMBOL_GPL(dccp_insert_option_timestamp);
-static int dccp_insert_option_timestamp_echo(struct sock *sk,
+static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
+ struct dccp_request_sock *dreq,
struct sk_buff *skb)
{
- struct dccp_sock *dp = dccp_sk(sk);
__be32 tstamp_echo;
- int len, elapsed_time_len;
unsigned char *to;
- const suseconds_t delta = ktime_us_delta(ktime_get_real(),
- dp->dccps_timestamp_time);
- u32 elapsed_time = delta / 10;
+ u32 elapsed_time, elapsed_time_len, len;
+
+ if (dreq != NULL) {
+ elapsed_time = dccp_timestamp() - dreq->dreq_timestamp_time;
+ tstamp_echo = htonl(dreq->dreq_timestamp_echo);
+ dreq->dreq_timestamp_echo = 0;
+ } else {
+ elapsed_time = dccp_timestamp() - dp->dccps_timestamp_time;
+ tstamp_echo = htonl(dp->dccps_timestamp_echo);
+ dp->dccps_timestamp_echo = 0;
+ }
+
elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
len = 6 + elapsed_time_len;
@@ -415,7 +434,6 @@
*to++ = DCCPO_TIMESTAMP_ECHO;
*to++ = len;
- tstamp_echo = htonl(dp->dccps_timestamp_echo);
memcpy(to, &tstamp_echo, 4);
to += 4;
@@ -427,8 +445,6 @@
memcpy(to, &var32, 4);
}
- dp->dccps_timestamp_echo = 0;
- dp->dccps_timestamp_time = ktime_set(0, 0);
return 0;
}
@@ -537,10 +553,6 @@
dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
dccp_insert_option_ackvec(sk, skb))
return -1;
-
- if (dp->dccps_timestamp_echo != 0 &&
- dccp_insert_option_timestamp_echo(sk, skb))
- return -1;
}
if (dp->dccps_hc_rx_insert_options) {
@@ -564,6 +576,10 @@
dccp_insert_option_timestamp(sk, skb))
return -1;
+ if (dp->dccps_timestamp_echo != 0 &&
+ dccp_insert_option_timestamp_echo(dp, NULL, skb))
+ return -1;
+
/* XXX: insert other options when appropriate */
if (DCCP_SKB_CB(skb)->dccpd_opt_len != 0) {