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[DCCP]: Provide function for RTT sampling

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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 commit is contained in:
Gerrit Renker 2007-03-20 15:23:18 -03:00 committed by David S. Miller
parent 0c150efb28
commit 4712a792ee
2 changed files with 48 additions and 2 deletions
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10
net/dccp/dccp.h
View file

@ -71,11 +71,15 @@ extern void dccp_time_wait(struct sock *sk, int state, int timeo);
/* RFC 1122, 4.2.3.1 initial RTO value */
#define DCCP_TIMEOUT_INIT ((unsigned)(3 * HZ))
#define DCCP_RTO_MAX ((unsigned)(120 * HZ)) /* FIXME: using TCP value */
/* bounds for sampled RTT values from packet exchanges (in usec) */
#define DCCP_SANE_RTT_MIN 100
#define DCCP_SANE_RTT_MAX (4 * USEC_PER_SEC)
/* Maximal interval between probes for local resources. */
#define DCCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ / 2U))
#define DCCP_RTO_MAX ((unsigned)(120 * HZ)) /* FIXME: using TCP value */
/* sysctl variables for DCCP */
extern int sysctl_dccp_request_retries;
extern int sysctl_dccp_retries1;
@ -292,6 +296,8 @@ extern int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
extern int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code);
extern void dccp_send_close(struct sock *sk, const int active);
extern int dccp_invalid_packet(struct sk_buff *skb);
extern u32 dccp_sample_rtt(struct sock *sk, struct timeval *t_recv,
struct timeval *t_history);
static inline int dccp_bad_service_code(const struct sock *sk,
const __be32 service)

40
net/dccp/input.c
View file

@ -577,3 +577,43 @@ discard:
}
EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
/**
* dccp_sample_rtt - Sample RTT from packet exchange
*
* @sk: connected dccp_sock
* @t_recv: receive timestamp of packet with timestamp echo
* @t_hist: packet history timestamp or NULL
*/
u32 dccp_sample_rtt(struct sock *sk, struct timeval *t_recv,
struct timeval *t_hist)
{
struct dccp_sock *dp = dccp_sk(sk);
struct dccp_options_received *or = &dp->dccps_options_received;
suseconds_t delta;
if (t_hist == NULL) {
if (!or->dccpor_timestamp_echo) {
DCCP_WARN("packet without timestamp echo\n");
return DCCP_SANE_RTT_MAX;
}
timeval_sub_usecs(t_recv, or->dccpor_timestamp_echo * 10);
delta = timeval_usecs(t_recv);
} else
delta = timeval_delta(t_recv, t_hist);
delta -= or->dccpor_elapsed_time * 10; /* either set or 0 */
if (unlikely(delta <= 0)) {
DCCP_WARN("unusable RTT sample %ld, using min\n", (long)delta);
return DCCP_SANE_RTT_MIN;
}
if (unlikely(delta - (suseconds_t)DCCP_SANE_RTT_MAX > 0)) {
DCCP_WARN("RTT sample %ld too large, using max\n", (long)delta);
return DCCP_SANE_RTT_MAX;
}
return delta;
}
EXPORT_SYMBOL_GPL(dccp_sample_rtt);