.NET MeetUp Prague, CZ - 2017/7/19 Talk: Portable .NET Core on Linux by Jan Vorlicek

1. Portable .NET Core on Linux
Jan Vorlicek
Microsoft

2. .NET Core on different Linux distros
• CoreCLR / CoreFX use several native platform libraries (standard
C/C++ libraries, CURL, ICU, SSL, …)
• Managed code calls to those via thin PAL layer
• Their SO names and supported APIs can differ per Linux distro or even
distro versions
• Native parts of CoreCLR / CoreFX built on one distro don‘t necessarily
work on others
• Targeting Linux if .NET Core native components are built as distro
dependent complicates building .NET Core apps

3. Making .NET Core on Linux portable
• Fixing issues with standard C/C++ libraries - build native components on
the oldest supported distro.
• Fixing issues with ICU / SSL / CURL
• Shims to load the 3rd party libraries and resolve their symbols.
• ICU – handle different SO name for each ICU version (libicuuc.so.52.1,
libicuuc.so.53.1, …). On most distros, the symbol names contain version number too
(u_strlen_52, u_strlen_52_1).
• SSL – handle different SO name on Fedora based distros (libssl.so.10) and different
one on the others (libssl.so.1.0.0). Debian 9 started to use libssl.so.1.0.2.
• SSL - optional usage of some elliptic curves cryptography functions.
• CURL – dynamic detection and optional handling of HTTP 2.0 request multiplexing.

4. Enabling standalone portable .NET Core apps
• Using the RPATH in the host executable (apphost)
• Set to $ORIGIN/netcoredeps
• Developers can create that subfolder next to the main executable and
store copies all native dependencies they want in there
• Linux loader looks into this folder when loading dependencies before
looking into standard locations
• It works transitively (for dependencies of these dependencies etc.)