[DCCP]: 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 <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>
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 292f18e..d8ad27b 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -71,11 +71,15 @@
/* 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_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)