Dummynet has a limit of 100 slots queue size (or 1MB, if you give

the limit in bytes) hard coded into both the kernel and userland.
Make both these limits a sysctl, so it is easy to change the limit.
If the userland part of ipfw finds that the sysctls don't exist,
it will just fall back to the traditional limits.

(100 packets is quite a small limit these days. If you want to test
TCP at 100Mbps, 100 packets can only accommodate a DBP of 12ms.)

Note these sysctls in the man page and warn against increasing them
without thinking first.

MFC after:      3 weeks

1 files changed, 14 insertions, 0 deletions

diff --git a/sbin/ipfw/ipfw.8 b/sbin/ipfw/ipfw.8
index fa7a0c5..7796005 100644
--- a/sbin/ipfw/ipfw.8
+++ b/sbin/ipfw/ipfw.8
@@ -1971,6 +1971,13 @@ or 20s of queue on a 30Kbit/s pipe.
 Even worse effects can result if you get packets from an
 interface with a much larger MTU, e.g.\& the loopback interface
 with its 16KB packets.
+The
+.Xr sysctl 8
+variables
+.Em net.inet.ip.dummynet.pipe_byte_limit
+and
+.Em net.inet.ip.dummynet.pipe_slot_limit
+control the maximum lengths that can be specified.
 .Pp
 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
 Make use of the RED (Random Early Detection) queue management algorithm.
@@ -2190,6 +2197,13 @@ will be expired even when
 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
 Parameters used in the computations of the drop probability
 for the RED algorithm.
+.It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
+.It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
+The maximum queue size that can be specified in bytes or packets.
+These limits prevent accidental exhaustion of resources such as mbufs.
+If you raise these limits,
+you should make sure the system is configured so that sufficient resources
+are available.
 .It Va net.inet.ip.fw.autoinc_step : No 100
 Delta between rule numbers when auto-generating them.
 The value must be in the range 1..1000.