Add a comment about how to tell this where to find pcap.

Most of the time this probably won't be an issue on UN*Xes, but it'll
probably be an issue on Windows.

diff --git a/cmake/Modules/FindPCAP.cmake b/cmake/Modules/FindPCAP.cmake
index 3b83c7a79fab45785ea6932df5f92251cab5d0b6..64d0901d126bf9d2300bf3d73b352de28e18fa75 100644 (file)
--- a/cmake/Modules/FindPCAP.cmake
+++ b/cmake/Modules/FindPCAP.cmake
@@ -1,6 +1,12 @@
 #
 # Try to find libpcap.
 #
+# To tell this module where to look, a user may set the environment variable
+# PCAP_ROOT to point cmake to the *root* of a directory with include and
+# lib subdirectories for pcap.dll (e.g WpdPack or npcap-sdk).
+# Alternatively, PCAP_ROOT may also be set from cmake command line or GUI
+# (e.g cmake -DPCAP_ROOT=C:\path\to\pcap [...])
+#
 
 if(WIN32)
   #