From b4d4f7c70fd3361c6c889752e08ea9be304cf5f4 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Thu, 13 Dec 2007 12:37:19 -0200 Subject: [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 Acked-by: Ian McDonald Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: David S. Miller --- net/dccp/options.c | 56 +++++++++++++++++++++++++++++++++++------------------- 1 file changed, 36 insertions(+), 20 deletions(-) (limited to 'net/dccp/options.c') diff --git a/net/dccp/options.c b/net/dccp/options.c index f496d4dc7efc..0c996d8c79a3 100644 --- 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) { -- cgit v1.2.3