Index: head/share/man/man4/netdump.4
===================================================================
--- head/share/man/man4/netdump.4
+++ head/share/man/man4/netdump.4
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 8, 2018
+.Dd October 29, 2018
 .Dt NETDUMP 4
 .Os
 .Sh NAME
@@ -130,6 +130,19 @@
 will cause the server to attempt to store dumps from the client in
 .Pa /var/crash/foo .
 The server will not automatically create the relative directory.
+.It Va net.netdump.polls
+The client will poll the configured network interface while waiting for
+acknowledgements.
+This parameter controls the maximum number of poll attempts before giving
+up, which typically results in a re-transmit.
+Each poll attempt takes 0.5ms.
+.It Va net.netdump.retries
+The number of times the client will re-transmit a packet before aborting
+a dump due to a lack of acknowledgement.
+The default may be too small in environments with lots of packet loss.
+.It Va net.netdump.arp_retries
+The number of times the client will attempt to learn the MAC address of
+the configured gateway or server before giving up and aborting the dump.
 .El
 .Sh SEE ALSO
 .Xr decryptcore 8 ,
Index: head/sys/netinet/netdump/netdump_client.c
===================================================================
--- head/sys/netinet/netdump/netdump_client.c
+++ head/sys/netinet/netdump/netdump_client.c
@@ -117,18 +117,6 @@
 static uint64_t rcvd_acks;
 CTASSERT(sizeof(rcvd_acks) * NBBY == NETDUMP_MAX_IN_FLIGHT);
 
-/*
- * Times to poll the NIC (0.5ms each poll) before assuming packetloss
- * occurred (default to 1s).
- */
-static int nd_polls = 2000;
-
-/* Times to retransmit lost packets. */
-static int nd_retries = 10;
-
-/* Number of ARP retries. */
-static int nd_arp_retries = 3;
-
 /* Configuration parameters. */
 static struct netdump_conf nd_conf;
 #define	nd_server	nd_conf.ndc_server
@@ -157,6 +145,18 @@
 SYSCTL_STRING(_net_netdump, OID_AUTO, path, CTLFLAG_RW,
     nd_path, sizeof(nd_path),
     "Server path for output files");
+static int nd_polls = 2000;
+SYSCTL_INT(_net_netdump, OID_AUTO, polls, CTLFLAG_RWTUN,
+    &nd_polls, 0,
+    "Number of times to poll before assuming packet loss (0.5ms per poll)");
+static int nd_retries = 10;
+SYSCTL_INT(_net_netdump, OID_AUTO, retries, CTLFLAG_RWTUN,
+    &nd_retries, 0,
+    "Number of retransmit attempts before giving up");
+static int nd_arp_retries = 3;
+SYSCTL_INT(_net_netdump, OID_AUTO, arp_retries, CTLFLAG_RWTUN,
+    &nd_arp_retries, 0,
+    "Number of ARP attempts before giving up");
 
 /*
  * Checks for netdump support on a network interface