: Provide function for RTT sampling
Subsystems (2)
PATCH 28/31 : Provide function for RTT sampling
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 <[email protected]>
Signed-off-by Ian McDonald <[email protected]>
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
--- net/dccp/dccp.h | 10 ++++++++-- net/dccp/input.c | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+), 2 deletions(-)
net/dccp/dccp.h +8 -2
@@ -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;
@@ -293,6 +297,8 @@ 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)
net/dccp/input.c +40 -0
@@ -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);
Signature · 1 line
1.5.0.3