#include <stdio.h>
#include <string.h>
#include <stdlib.h>
+#include <fcntl.h>
+#include <string.h>
+#include <time.h>
+#include <arpa/inet.h>
+#include <sys/mman.h>
#include "pppd-private.h"
#include "options.h"
static void lcp_delayed_up(void *);
+/*
+ * These definitions relate to the measurement and logging of round-trip
+ * time (RTT) of LCP echo-requests implemented in lcp_rtt_update_buffer().
+ */
+#define LCP_RTT_MAGIC 0x19450425
+#define LCP_RTT_HEADER_LENGTH 4
+#define LCP_RTT_FILE_SIZE 8192
+#define LCP_RTT_ELEMENTS (LCP_RTT_FILE_SIZE / sizeof(u_int32_t) - LCP_RTT_HEADER_LENGTH) / 2
+
/*
* LCP-related command-line options.
*/
int lcp_echo_interval = 0; /* Interval between LCP echo-requests */
int lcp_echo_fails = 0; /* Tolerance to unanswered echo-requests */
bool lcp_echo_adaptive = 0; /* request echo only if the link was idle */
+char *lcp_rtt_file = NULL; /* measure the RTT of LCP echo-requests */
bool lax_recv = 0; /* accept control chars in asyncmap */
bool noendpoint = 0; /* don't send/accept endpoint discriminator */
"Set time in seconds between LCP echo requests", OPT_PRIO },
{ "lcp-echo-adaptive", o_bool, &lcp_echo_adaptive,
"Suppress LCP echo requests if traffic was received", 1 },
+ { "lcp-rtt-file", o_string, &lcp_rtt_file,
+ "Filename for logging the round-trip time of LCP echo requests",
+ OPT_PRIO | OPT_PRIV },
{ "lcp-restart", o_int, &lcp_fsm[0].timeouttime,
"Set time in seconds between LCP retransmissions", OPT_PRIO },
{ "lcp-max-terminate", o_int, &lcp_fsm[0].maxtermtransmits,
static int lcp_echos_pending = 0; /* Number of outstanding echo msgs */
static int lcp_echo_number = 0; /* ID number of next echo frame */
static int lcp_echo_timer_running = 0; /* set if a timer is running */
+static int lcp_rtt_file_fd = 0; /* fd for the opened LCP RTT file */
+static volatile u_int32_t *lcp_rtt_buffer = NULL; /* the mmap'ed LCP RTT file */
static u_char nak_buffer[PPP_MRU]; /* where we construct a nak packet */
}
}
+/*
+ * Log the round-trip time (RTT) of the received LCP echo-request.
+ *
+ * The header section at the beginning of lcp_rtt_file contains
+ * LCP_RTT_HEADER_LENGTH fields, each a u_int32_t in network byte order:
+ * [0] LCP_RTT_MAGIC
+ * [1] status (1: the file is open and is being written)
+ * [2] index of the most recently updated element
+ * [3] the value of the lcp-echo-interval parameter
+ *
+ * The header is followed by a ring buffer of LCP_RTT_ELEMENTS elements, each
+ * containing a pair of u_int32_t in network byte order with this content:
+ * [0] UNIX timestamp
+ * [1] bits 24-31: the number of lost LCP echo replies
+ * bits 0-23: the measured RTT in microseconds
+ *
+ * The timestamp is unsigned to support storing dates beyond 2038.
+ *
+ * Consumers of lcp_rtt_file are expected to:
+ * - read the complete file of arbitrary length
+ * - check the magic number
+ * - process the data elements starting at the index
+ * - ignore any elements with a timestamp of 0
+ */
+static void
+lcp_rtt_update_buffer (unsigned long rtt)
+{
+ volatile u_int32_t *const ring_buffer = lcp_rtt_buffer
+ + LCP_RTT_HEADER_LENGTH;
+ unsigned int next_entry, lost;
+
+ /* choose the next entry where the data will be stored */
+ if (ntohl(lcp_rtt_buffer[2]) >= (LCP_RTT_ELEMENTS - 1) * 2)
+ next_entry = 0; /* go back to the beginning */
+ else
+ next_entry = ntohl(lcp_rtt_buffer[2]) + 2; /* use the next one */
+
+ /* update the data element */
+ /* storing the timestamp in an *unsigned* long allows dates up to 2106 */
+ ring_buffer[next_entry] = htonl((u_int32_t) time(NULL));
+ lost = lcp_echos_pending - 1;
+ if (lost > 0xFF)
+ lost = 0xFF; /* truncate the lost packets count to 256 */
+ if (rtt > 0xFFFFFF)
+ rtt = 0xFFFFFF; /* truncate the RTT to 16777216 */
+ /* use bits 24-31 for the lost packets count and bits 0-23 for the RTT */
+ ring_buffer[next_entry + 1] = htonl((u_int32_t) ((lost << 24) + rtt));
+
+ /* update the pointer to the (just updated) most current data element */
+ lcp_rtt_buffer[2] = htonl(next_entry);
+
+ /* In theory, CPUs implementing a weakly-consistent memory model do not
+ * guarantee that these three memory store operations to the buffer will
+ * be seen in the same order by the reader process.
+ * This means that a process reading the file could see the index
+ * having been updated before the element that the index points to had
+ * been written.
+ * But in practice we expect that the read(2) system call used by
+ * consumers processes is atomic with respect to the following msync(2)
+ * call, so we ignore the issue.
+ */
+
+ if (msync(lcp_rtt_buffer, LCP_RTT_FILE_SIZE, MS_ASYNC) < 0)
+ error("msync() for %s failed: %m", lcp_rtt_file);
+}
+
/*
* LcpEchoReply - LCP has received a reply to the echo
*/
return;
}
+ if (lcp_rtt_file_fd && len >= 16) {
+ long lcp_rtt_magic;
+
+ /*
+ * If the magic word is found at the beginning of the data section
+ * of the frame then read the timestamp which follows and subtract
+ * it from the current time to compute the round trip time.
+ */
+ GETLONG(lcp_rtt_magic, inp);
+ if (lcp_rtt_magic == LCP_RTT_MAGIC) {
+ struct timespec ts;
+ unsigned long req_sec, req_nsec, rtt;
+
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+ GETLONG(req_sec, inp);
+ GETLONG(req_nsec, inp);
+ /* compute the RTT in microseconds */
+ rtt = (ts.tv_sec - req_sec) * 1000000
+ + (ts.tv_nsec / 1000 - req_nsec / 1000);
+ /* log the RTT */
+ lcp_rtt_update_buffer(rtt);
+ }
+ }
+
/* Reset the number of outstanding echo frames */
lcp_echos_pending = 0;
}
LcpSendEchoRequest (fsm *f)
{
u_int32_t lcp_magic;
- u_char pkt[4], *pktp;
+ u_char pkt[16], *pktp;
/*
* Detect the failure of the peer at this point.
lcp_magic = lcp_gotoptions[f->unit].magicnumber;
pktp = pkt;
PUTLONG(lcp_magic, pktp);
+
+ /* Put a timestamp in the data section of the frame */
+ if (lcp_rtt_file_fd) {
+ struct timespec ts;
+
+ PUTLONG(LCP_RTT_MAGIC, pktp);
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+ PUTLONG((u_int32_t)ts.tv_sec, pktp);
+ PUTLONG((u_int32_t)ts.tv_nsec, pktp);
+ }
+
fsm_sdata(f, ECHOREQ, lcp_echo_number++ & 0xFF, pkt, pktp - pkt);
++lcp_echos_pending;
}
}
+static void
+lcp_rtt_open_file (void)
+{
+ if (!lcp_rtt_file)
+ return;
+
+ lcp_rtt_file_fd = open(lcp_rtt_file, O_RDWR | O_CREAT, 0644);
+ if (lcp_rtt_file_fd < 0) {
+ error("Can't open the RTT log file %s: %m", lcp_rtt_file);
+ lcp_rtt_file_fd = 0;
+ return;
+ }
+
+ if (ftruncate(lcp_rtt_file_fd, LCP_RTT_FILE_SIZE) < 0)
+ fatal("ftruncate() of %s failed: %m", lcp_rtt_file);
+ lcp_rtt_buffer = mmap(0, LCP_RTT_FILE_SIZE, PROT_READ | PROT_WRITE,
+ MAP_SHARED, lcp_rtt_file_fd, 0);
+ if (lcp_rtt_buffer == MAP_FAILED)
+ fatal("mmap() of %s failed: %m", lcp_rtt_file);
+
+ /* initialize the ring buffer */
+ if (lcp_rtt_buffer[0] != htonl(LCP_RTT_MAGIC)) {
+ memset(lcp_rtt_buffer, 0, LCP_RTT_FILE_SIZE);
+ lcp_rtt_buffer[0] = htonl(LCP_RTT_MAGIC);
+ }
+
+ lcp_rtt_buffer[3] = htonl(lcp_echo_interval);
+ lcp_rtt_buffer[1] = htonl(1); /* status: LCP up, file opened */
+}
+
+static void
+lcp_rtt_close_file (void)
+{
+ if (!lcp_rtt_file_fd)
+ return;
+
+ lcp_rtt_buffer[1] = htonl(0); /* status: LCP down, file closed */
+
+ if (munmap(lcp_rtt_buffer, LCP_RTT_FILE_SIZE) < 0)
+ error("munmap() of %s failed: %m", lcp_rtt_file);
+ if (close(lcp_rtt_file_fd) < 0)
+ error("close() of %s failed: %m", lcp_rtt_file);
+ lcp_rtt_buffer = NULL;
+ lcp_rtt_file_fd = 0;
+}
+
/*
* lcp_echo_lowerup - Start the timer for the LCP frame
*/
lcp_echos_pending = 0;
lcp_echo_number = 0;
lcp_echo_timer_running = 0;
+
+ /* Open the file where the LCP RTT data will be logged */
+ lcp_rtt_open_file();
/* If a timeout interval is specified then start the timer */
if (lcp_echo_interval != 0)
UNTIMEOUT (LcpEchoTimeout, f);
lcp_echo_timer_running = 0;
}
+
+ /* Close the file containing the LCP RTT data */
+ lcp_rtt_close_file();
}
projects / ppp.git / commitdiff