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Wednesday, October 09, 2013

A Window into porting BGPDump

After reading about injecting BGP prefixes into a GNS3 simulation, I was eager to test it. I went looking for BGPDump and found it was only available for Linux. The source files made no mention of building on Win32.

I've ported Linux "only" - that is, source that provides no Win32-specific directives, code and / or headers - to Windows by editing the source. Network applications - those that use the Linux network headers and the Winsock headers in Windows - are much more difficult. I wasn't going to try this one. I figured I could compile under Cygwin and just have the cygwin1.dll dependency.

I don't normally run Cygwin; instead, I use the Win32 native ports found at GnuWin32. I have them all in my C:\usr\bin directory - the first in my PATH - and also a copy of the cygwin1.dll in that directory for the few programs that need it (namely iperf.exe - again built under Cygwin due to the complex network headers and porting issues).

So I used my Windows Virtual PC that has Cygwin installed, downloaded the latest copy of BGPDump (version / 21-Oct-2010 11:30 / 82K) and set to compiling it. The './configure' step went well. The 'make' not so much. I was missing some libraries, but the error messages were pretty obvious which ones were needed so I quickly re-ran the Cygwin setup - which also functions as a package manager - and installed the missing development libraries. Namely:

  • libzip-devel
  • libbz2-devel

I re-ran the build process and was done! I copied my C:\cygwin\bin\cygwin1.dll to the build directory and ran bgpdump.exe and it failed! Because it linked with those compression libraries, I also needed those DLL's as well as the libc DLL for Cygwin (cyggcc_s-1.dll). This was going to require an extra step. I needed to statically link the compression and libc libraries so the only dynamic dependency would be cygwin1.dll.

Looking at the 'make' output, I simply needed to modify the last build instruction from:

gcc -fPIC -g -O3 -Wall -Wsystem-headers -Wno-format-y2k -Wno-sign-compare -Wcast-align -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wswitch -Wshadow  -o bgpdump bgpdump.c libbgpdump.a -lbz2 -lz


gcc -fPIC -g -O3 -Wall -Wsystem-headers -Wno-format-y2k -Wno-sign-compare -Wcast-align -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wswitch -Wshadow  -o bgpdump bgpdump.c libbgpdump.a -Wl,-Bstatic -lbz2 -lz -static-libgcc

I added the "-Wl,-Bstatic" option before the compression libraries and the "-static-libgcc" option to statically link libc. I ran that command and now bgpdump.exe works with only the cygwin1.dll dependency.

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