Update epair(4) to the new netisr implementation and polish

things a bit:
- use dpcpu data to track the ifps with packets queued up,
- per-cpu locking and driver flags
- along with .nh_drainedcpu and NETISR_POLICY_CPU.
- Put the mbufs in flight reference count, preventing interfaces
  from going away, under INVARIANTS as this is a general problem
  of the stack and should be solved in if.c/netisr but still good
  to verify the internal queuing logic.
- Permit changing the MTU to virtually everythinkg like we do for loopback.

Hook epair(4) up to the build.

Approved by:	re (kib)

4 files changed, 10 insertions, 5 deletions

diff --git a/share/man/man4/Makefile b/share/man/man4/Makefile
index 973be6b..36d8928 100644
--- a/share/man/man4/Makefile
+++ b/share/man/man4/Makefile
@@ -94,6 +94,7 @@ MAN=	aac.4 \
 	em.4 \
 	en.4 \
 	enc.4 \
+	epair.4 \
 	esp.4 \
 	et.4 \
 	exca.4 \
@@ -490,6 +491,7 @@ MLINKS+=ef.4 if_ef.4
 MLINKS+=em.4 if_em.4
 MLINKS+=en.4 if_en.4
 MLINKS+=enc.4 if_enc.4
+MLINKS+=epair.4 if_epair.4
 MLINKS+=et.4 if_et.4
 MLINKS+=faith.4 if_faith.4
 MLINKS+=fatm.4 if_fatm.4
diff --git a/share/man/man4/altq.4 b/share/man/man4/altq.4
index c14fa49..55fb8c1 100644
--- a/share/man/man4/altq.4
+++ b/share/man/man4/altq.4
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 14, 2009
+.Dd July 26, 2009
 .Dt ALTQ 4
 .Os
 .Sh NAME
@@ -131,6 +131,7 @@ They have been applied to the following hardware drivers:
 .Xr ed 4 ,
 .Xr em 4 ,
 .Xr ep 4 ,
+.Xr epair 4 ,
 .Xr fxp 4 ,
 .Xr gem 4 ,
 .Xr hme 4 ,
diff --git a/share/man/man4/epair.4 b/share/man/man4/epair.4
index b93d36e..8b4d140 100644
--- a/share/man/man4/epair.4
+++ b/share/man/man4/epair.4
@@ -28,12 +28,12 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 15, 2008
+.Dd July 26, 2009
 .Dt EPAIR 4
 .Os
 .Sh NAME
 .Nm epair
-.Nd Virtual cross-over Ethernet-like interface pair.
+.Nd A pair of virtual back-to-back connected Ethernet interfaces.
 .Sh SYNOPSIS
 To compile this driver into the kernel,
 place the following line in your
@@ -52,7 +52,7 @@ if_epair_load="YES"
 The
 .Nm
 is a pair of Ethernet-like software interfaces,
-which are directly connected by a virtual cross-over cable.
+which are connected back-to-back with a virtual cross-over cable.
 .Pp
 Each
 .Nm
diff --git a/share/man/man9/netisr.9 b/share/man/man9/netisr.9
index b4062e0..ed2a84e 100644
--- a/share/man/man9/netisr.9
+++ b/share/man/man9/netisr.9
@@ -27,7 +27,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 14, 2009
+.Dd July 26, 2009
 .Dt NETISR 9
 .Os
 .Sh NAME
@@ -208,6 +208,8 @@ IPX/SPX
 IPv6
 .It Dv NETISR_NATM
 ATM
+.It Dv NETISR_EPAIR
+.Xr epair 4
 .El
 .Sh AUTHORS
 This manual page and the