Document background noise of RX packets from bridges (RHBZ#647987).

[virt-top.git] / virt-top / virt-top.1

diff --git a/virt-top/virt-top.1 b/virt-top/virt-top.1
index 1cd5843..2665e27 100755 (executable)
--- a/virt-top/virt-top.1
+++ b/virt-top/virt-top.1
@@ -437,6 +437,20 @@ init file.
 Note that in the current implementation, options specified in
 the init file override options specified on the command line.
 This is a bug and this behaviour may change in the future.
 Note that in the current implementation, options specified in
 the init file override options specified on the command line.
 This is a bug and this behaviour may change in the future.

+.SH "NOTES"
+.IX Header "NOTES"
+.SS "\s-1NETWORK\s0 \s-1RX\s0 \s-1BYTES\s0 \s-1AND\s0 \s-1PACKETS\s0"
+.IX Subsection "NETWORK RX BYTES AND PACKETS"
+Libvirt/virt\-top has no way to know that a packet transmitted to a
+guest was received (eg. if the guest is not listening).  In the
+network \s-1RX\s0 stats, virt-top reports the packets transmitted to the
+guest, on the basis that the guest might receive them.
+.PP
+In particular this includes broadcast packets.  Because of the way
+that Linux bridges work, if the guest is connected to a bridge, it
+will probably see a steady \*(L"background noise\*(R" of \s-1RX\s0 packets even when
+the network interface is idle or down.  These are caused by \s-1STP\s0
+packets generated by the bridge.

 .SH "SEE ALSO"
 .IX Header "SEE ALSO"
 \&\fItop\fR\|(1),
 .SH "SEE ALSO"
 .IX Header "SEE ALSO"
 \&\fItop\fR\|(1),