guyharris
commented
3 years ago In
New in macOS Big Sur 11.0.1, the system ships with a built-in dynamic linker cache of all system-provided libraries. As part of this change, copies of dynamic libraries are no longer present on the filesystem. Code that attempts to check for dynamic library presence by looking for a file at a path or enumerating a directory will fail. Instead, check for library presence by attempting to dlopen() the path, which will correctly check for the library in the cache. (62986286)
the dlopen() alternative is "you attempt to determine whether you can use the library by attempting to use the library, rather than by some other technique making an assumption about how the library is implemented".
So one alternative would be to modify find_lib_path_and_file() to use dlopen() on most UN*Xes (with the exception of 32-bit HP-UX) and LoadLibrary() on Windows. Older versions of some UN*Xes might not support dlopen()ing shared libraries (Mach-O has separate file types for shared libraries and dynamically-loaded files - newer versions of macOS treat them the same, but older versions may treat them differently), so both attempting to load the library through the official system API and looking for the file might be necessary.
(Can ctypes be used?)
Another alternative would be "Apple's shipped libpcap and tcpdump since Day One, or close to it, so we'll just assume we have it". If that's too risky, you could try running the command
otool -L `which tcpdump`from the setup script if you're on macOS, and capture its output, to 1) find tcpdump and 2) get the paths of the libraries it has to load; on my 11.2.3 (x86-64) VM, it prints:
/usr/sbin/tcpdump:
/usr/lib/libssl.46.dylib (compatibility version 47.0.0, current version 47.1.0)
/usr/lib/libcrypto.44.dylib (compatibility version 45.0.0, current version 45.1.0)
/usr/lib/libpcap.A.dylib (compatibility version 1.0.0, current version 1.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1292.60.1)
phunkyg
mwfong-csl
slhck
koczanm
tulay
Attempting to use pypcap under python 2.7 installing via pip.
None of the following found: ['libpcap.a', 'libpcap.so', 'libpcap.dylib', 'wpcap.lib']Appears to be related to the changes introduced in Big Sur that means the .dylib files no longer exist, they are all part of the new dynamic cache.
For example, here is the homebrew project having the same: https://github.com/Homebrew/brew/issues/7803 Another: https://github.com/openframeworks/openFrameworks/issues/6599#issuecomment-691685881 More: https://mjtsai.com/blog/2020/06/26/reverse-engineering-macos-11-0/
The Apple release note having the info: https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11_0_1-release-notes
Understandably being as Apple are moving things and changing the norms, lots of this kind of thing are going to break. Looking for a workaround if possible or a fix that implements the dlopen() alternative - whatever that means!