[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/include/linux/dccp.h b/include/linux/dccp.h
index 7214031461d3b190d086dd74dc31fad05de850fb..484e45c7c89a832dd986c7fe927e545168e2ec77 100644 (file)
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -407,11 +407,23 @@ struct dccp_opt_pend {
 
 extern void dccp_minisock_init(struct dccp_minisock *dmsk);
 
+/**
+ * struct dccp_request_sock  -  represent DCCP-specific connection request
+ * @dreq_inet_rsk: structure inherited from
+ * @dreq_iss: initial sequence number sent on the Response (RFC 4340, 7.1)
+ * @dreq_isr: initial sequence number received on the Request
+ * @dreq_service: service code present on the Request (there is just one)
+ * The following two fields are analogous to the ones in dccp_sock:
+ * @dreq_timestamp_echo: last received timestamp to echo (13.1)
+ * @dreq_timestamp_echo: the time of receiving the last @dreq_timestamp_echo
+ */
 struct dccp_request_sock {
        struct inet_request_sock dreq_inet_rsk;
        __u64                    dreq_iss;
        __u64                    dreq_isr;
        __be32                   dreq_service;
+       __u32                    dreq_timestamp_echo;
+       __u32                    dreq_timestamp_time;
 };
 
 static inline struct dccp_request_sock *dccp_rsk(const struct request_sock *req)
@@ -477,8 +489,8 @@ struct dccp_ackvec;
  * @dccps_gar - greatest valid ack number received on a non-Sync; initialized to %dccps_iss
  * @dccps_service - first (passive sock) or unique (active sock) service code
  * @dccps_service_list - second .. last service code on passive socket
- * @dccps_timestamp_time - time of latest TIMESTAMP option
  * @dccps_timestamp_echo - latest timestamp received on a TIMESTAMP option
+ * @dccps_timestamp_time - time of receiving latest @dccps_timestamp_echo
  * @dccps_l_ack_ratio - feature-local Ack Ratio
  * @dccps_r_ack_ratio - feature-remote Ack Ratio
  * @dccps_pcslen - sender   partial checksum coverage (via sockopt)
@@ -514,8 +526,8 @@ struct dccp_sock {
        __u64                           dccps_gar;
        __be32                          dccps_service;
        struct dccp_service_list        *dccps_service_list;
-       ktime_t                         dccps_timestamp_time;
        __u32                           dccps_timestamp_echo;
+       __u32                           dccps_timestamp_time;
        __u16                           dccps_l_ack_ratio;
        __u16                           dccps_r_ack_ratio;
        __u16                           dccps_pcslen;

diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index b1d5da61f6afbf29ce7a9a3e13cc83bbd084efa5..027d1814e1ab39da6efdc7cceead60ac38c01fe8 100644 (file)
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -117,11 +117,13 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
                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;
-               newdp->dccps_service_list  = NULL;
-               newdp->dccps_service       = dreq->dreq_service;
-               newicsk->icsk_rto          = DCCP_TIMEOUT_INIT;
+               newdp->dccps_role           = DCCP_ROLE_SERVER;
+               newdp->dccps_hc_rx_ackvec   = NULL;
+               newdp->dccps_service_list   = NULL;
+               newdp->dccps_service        = dreq->dreq_service;
+               newdp->dccps_timestamp_echo = dreq->dreq_timestamp_echo;
+               newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;
+               newicsk->icsk_rto           = DCCP_TIMEOUT_INIT;
 
                if (dccp_feat_clone(sk, newsk))
                        goto out_free;
@@ -303,9 +305,12 @@ EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack);
 
 void dccp_reqsk_init(struct request_sock *req, struct sk_buff *skb)
 {
-       inet_rsk(req)->rmt_port = dccp_hdr(skb)->dccph_sport;
-       inet_rsk(req)->acked    = 0;
-       req->rcv_wnd            = sysctl_dccp_feat_sequence_window;
+       struct dccp_request_sock *dreq = dccp_rsk(req);
+
+       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_timestamp_echo = 0;
 }
 
 EXPORT_SYMBOL_GPL(dccp_reqsk_init);

diff --git a/net/dccp/options.c b/net/dccp/options.c
index f496d4dc7efcf760fe1d67f210da4431939643e2..0c996d8c79a31a0ae82de53ffc61d887e231061f 100644 (file)
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -166,16 +166,27 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
                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);
-
-                       /* 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 (unlikely(opt_val == 0)) {
+                               DCCP_WARN("Timestamp with zero value\n");
+                               break;
+                       }
 
+                       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 @@ int dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
 
 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 @@ static int dccp_insert_option_timestamp_echo(struct sock *sk,
        *to++ = DCCPO_TIMESTAMP_ECHO;
        *to++ = len;
 
-       tstamp_echo = htonl(dp->dccps_timestamp_echo);
        memcpy(to, &tstamp_echo, 4);
        to += 4;
 
@@ -427,8 +445,6 @@ static int dccp_insert_option_timestamp_echo(struct sock *sk,
                memcpy(to, &var32, 4);
        }
 
-       dp->dccps_timestamp_echo = 0;
-       dp->dccps_timestamp_time = ktime_set(0, 0);
        return 0;
 }
 
@@ -537,10 +553,6 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
                    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 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
            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) {