Implement ISOBUS File Server (FS) Interface as a Personal Project

Introduce the ISOBUS File Server (FS) interface, compatible with ISO
11783-13. The implementation utilizes the kernel's existing CAN J1939
socket support.

For testing following setup can be used:
ip link add type vcan
ip l s dev vcan0 up

j1939acd -r 64-95 -c /tmp/1122334455667788.jacd 1122334455667788 vcan0 &
j1939acd -r 96-127 -c /tmp/1122334455667789.jacd 1122334455667789 vcan0 &

sleep 1

isobusfs-srv -i vcan0 -n 1122334455667788 -v vol1:/path/to/export/
isobusfs-cli -i vcan0 -n 0x1122334455667789 -m 0x1122334455667788 -I

Interactive mode currently support following commands:
exit - exit interactive mode
quit - exit interactive mode
help - show this help
dmesg - show log buffer
selftest - run selftest
ls - list directory
ll - list directory with long listing format
cd - change directory
pwd - print name of current/working directory
get - get file

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>

isobusfs/isobusfs_create_test_dirs.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+
+mkdir dir1
+mkdir dir1/dir2
+mkdir dir1/dir2/dir3
+mkdir dir1/dir2/dir3/dir4
+mkdir dir1/dir2/dir3/dir5
+mkdir MCMC0683
+mkdir MCMC0683/msd_dir1/msd_dir2
+mkdir MCMC0683/msd_dir1/msd_dir2/~
+mkdir MCMC0683/msd_dir1/msd_dir2/~/~tilde_dir
+mkdir dir1/~
+mkdir dir1/~/~
+
+echo "hello" > dir1/dir2/file0
+
+./isobusfs_create_test_file.sh dir1/dir2/file1k 1024
+./isobusfs_create_test_file.sh dir1/dir2/file1m 1048576
+
+ File and directory names testing
+mkdir 'dir1/dir2/special_chars_*?/'
+mkdir 'dir1/dir2/unicode_名字'
+
+# Define the long suffix for the filenames
+long_suffix="abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnop"
+
+# Loop to create 300 files with long names
+for count in {1..300}; do
+    touch "long_name_${count}_${long_suffix}"
+done
+
+touch dir1/dir2/hidden_file
+touch dir1/dir2/readonly_file
+touch dir1/dir2/executable_file
+touch dir1/dir2/no_read_permission_file
+
+# Setting permissions
+chmod 444 dir1/dir2/readonly_file  # Read-only file
+chmod +x dir1/dir2/executable_file  # Executable file
+chmod 000 dir1/dir2/no_read_permission_file  # No read permission for anyone
+
+# Create directories for date problems
+mkdir "dir1/dir2/y2000_problem"
+mkdir "dir1/dir2/y2038_problem"
+mkdir "dir1/dir2/y1979_problem"
+mkdir "dir1/dir2/y1980_problem"
+mkdir "dir1/dir2/y2107_problem"
+mkdir "dir1/dir2/y2108_problem"
+
+# Change timestamps to reflect specific years
+# Year 2000
+touch -d '2000-01-01 00:00:00' dir1/dir2/y2000_problem
+
+# Year 2038 - beyond 19 January 2038, Unix timestamp issue
+touch -d '2038-01-20 00:00:00' dir1/dir2/y2038_problem
+
+# Year 1980 - minimal year supported
+touch -d '1979-12-31 23:59:59' dir1/dir2/y1979_problem
+touch -d '1980-01-01 00:00:00' dir1/dir2/y1980_problem
+
+# Year 2107 - max year 1980+127
+touch -d '2107-12-31 23:59:59' dir1/dir2/y2107_problem
+touch -d '2108-01-01 00:00:00' dir1/dir2/y2108_problem
+