Tiny TCP

For build prereqs, see the CS144 VM setup instructions.

Sponge quickstart

To set up your build directory:

$ mkdir -p <path/to/sponge>/build
$ cd <path/to/sponge>/build
$ cmake ..

Note: all further commands listed below should be run from the build dir.

To build:

$ make

You can use the -j switch to build in parallel, e.g.,

$ make -j$(nproc)

To test (after building; make sure you've got the build prereqs installed!)

$ make check

The first time you run make check, it will run sudo to configure two TUN devices for use during testing.

build options

You can specify a different compiler when you run cmake:

$ CC=clang CXX=clang++ cmake ..

You can also specify CLANG_TIDY= or CLANG_FORMAT= (see "other useful targets", below).

Sponge's build system supports several different build targets. By default, cmake chooses the Release target, which enables the usual optimizations. The Debug target enables debugging and reduces the level of optimization. To choose the Debug target:

$ cmake .. -DCMAKE_BUILD_TYPE=Debug

The following targets are supported:

• Release - optimizations
• Debug - debug symbols and -Og
• RelASan - release build with ASan and UBSan
• RelTSan - release build with ThreadSan
• DebugASan - debug build with ASan and UBSan
• DebugTSan - debug build with ThreadSan

Of course, you can combine all of the above, e.g.,

$ CLANG_TIDY=clang-tidy-6.0 CXX=clang++-6.0 .. -DCMAKE_BUILD_TYPE=Debug

Note: if you want to change CC, CXX, CLANG_TIDY, or CLANG_FORMAT, you need to remove build/CMakeCache.txt and re-run cmake. (This isn't necessary for CMAKE_BUILD_TYPE.)

other useful targets

To generate documentation (you'll need doxygen; output will be in build/doc/):

$ make doc

To lint (you'll need clang-tidy):

$ make -j$(nproc) tidy

To run cppcheck (you'll need cppcheck):

$ make cppcheck

To format (you'll need clang-format):

$ make format

To see all available targets,

$ make help

Configuration

Tests associating with full TCPConnection and NetworkInterface would require some NAT rules in iptables, as scripted in tap.sh and tun.sh. Beforing running these tests, make sure that the original iptable rules will not conflict with rules added by these scripts. After running the scripts, make sure that the rules are effective and makes sense. For example, the NAT rule should produce a proper IP address for your TCPSegments so that other hosts can reach you. Otherwise, you won't get any response even if your implementation is correct.

I modified these scripts with simple rules below to make NAT work in WSL:

# tap.sh
HOST=172.233.233.233 # ip address that makes sense
iptables -t nat -A PREROUTING -s ${HOST} -j DNAT --to-destination ${TUN_IP_PREFIX}.${TAPNUM}.9
iptables -t nat -A POSTROUTING -s ${TUN_IP_PREFIX}.${1}.0/24 -j SNAT --to-source ${HOST}