Add mpath to ip manpage.

From: Norbert Buchmuller <norbi@nix.hu>

The 'mpath' parameter of 'ip route' is not documented in the manual page
nor in ip-cref.tex.

...huge part of the text in the patch was taken from the net/ipv4/Kconfig
file in the Linux kernel source (2.6.18). I suppose that's OK because both
Linux and iproute2 are GPL'd, but I let you know anyway.

See Debian bug #428442 - http://bugs.debian.org/428442

diff -Naur iproute-20061002/doc/ip-cref.tex iproute-20061002.fixed/doc/ip-cref.tex
--- iproute-20061002/doc/ip-cref.tex	2007-06-11 19:26:52.000000000 +0200
+++ iproute-20061002.fixed/doc/ip-cref.tex	2007-06-11 20:34:09.000000000 +0200
@@ -1348,6 +1348,28 @@
 route reflecting its relative bandwidth or quality.
 \end{itemize}
 
+\item \verb|mpath MP_ALGO|
+
+--- the  multipath algo to use.
+\verb|MP_ALGO| may be one of the following values:
+\begin{itemize}
+\item \verb|rr| --- round robin algorithm.
+Multipath routes are chosen according to Round Robin.
+\item \verb|drr| --- interface round robin algorithm.
+Connections are distributed in a round robin fashion over the
+available interfaces. This policy makes sense if the connections 
+should be primarily distributed on interfaces and not on routes.
+\item \verb|random| --- random algorithm.
+Multipath routes are chosen in a random fashion. Actually,
+there is no weight for a route. The advantage of this policy
+is that it is implemented stateless and therefore introduces only
+a very small delay.
+\item \verb|wrandom| --- weighted random algorithm.
+Multipath routes are chosen in a weighted random fashion. 
+The per route weights are the weights visible via ip route 2. As the
+corresponding state management introduces some overhead routing delay
+is increased.
+\end{itemize}
 \item \verb|scope SCOPE_VAL|
 
 --- the scope of the destinations covered by the route prefix.
diff -Naur iproute-20061002/man/man8/ip.8 iproute-20061002.fixed/man/man8/ip.8
--- iproute-20061002/man/man8/ip.8	2007-06-11 19:26:52.000000000 +0200
+++ iproute-20061002.fixed/man/man8/ip.8	2007-06-11 20:26:43.000000000 +0200
@@ -146,7 +146,9 @@
 .B  scope
 .IR SCOPE " ] [ "
 .B  metric
-.IR METRIC " ]"
+.IR METRIC " ] [ "
+.B  mpath
+.IR MP_ALGO " ]"
 
 .ti -8
 .IR INFO_SPEC " := " "NH OPTIONS FLAGS" " ["
@@ -205,6 +207,10 @@
 .BR onlink " | " pervasive " ]"
 
 .ti -8
+.IR MP_ALGO " := [ "
+.BR rr " | " drr " | " random " | " wrandom " ]"
+
+.ti -8
 .IR RTPROTO " := [ "
 .BR kernel " | " boot " | " static " |"
 .IR NUMBER " ]"
@@ -1116,6 +1122,38 @@
 .in -8
 
 .TP
+.BI mpath " MP_ALGO"
+the multipath algo to use.
+.I MP_ALGO
+may be one of the following values:
+
+.in +8
+.B rr
+- round robin algorithm.
+Multipath routes are chosen according to Round Robin.
+.sp
+.B drr
+- interface round robin algorithm.
+Connections are distributed in a round robin fashion over the
+available interfaces. This policy makes sense if the connections 
+should be primarily distributed on interfaces and not on routes.
+.sp
+.B random
+- random algorithm.
+Multipath routes are chosen in a random fashion. Actually,
+there is no weight for a route. The advantage of this policy
+is that it is implemented stateless and therefore introduces only
+a very small delay.
+.sp
+.B wrandom
+- weighted random algorithm.
+Multipath routes are chosen in a weighted random fashion. 
+The per route weights are the weights visible via ip route 2. As the
+corresponding state management introduces some overhead routing delay
+is increased.
+.in -8
+
+.TP
 .BI scope " SCOPE_VAL"
 the scope of the destinations covered by the route prefix.
 .I SCOPE_VAL