+
+Reproducing issues
+==================
+
+If a fuzzer generates a reproducible error, you can reproduce the problem using
+the fuzz/*-test binaries and the file generated by the fuzzer. They binaries
+don't need to be build for fuzzing, there is no need to set CC or the call
+config with enable-fuzz-* or -fsanitize-coverage, but some of the other options
+above might be needed. For instance the enable-asan or enable-ubsan option might
+be useful to show you when the problem happens. For the client and server fuzzer
+it might be needed to use -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION to
+reproduce the generated random numbers.
+
+To reproduce the crash you can run:
+
+ $ fuzz/$FUZZER-test $file
+
+Random numbers
+==============
+
+The client and server fuzzer normally generate random numbers as part of the TLS
+connection setup. This results in the coverage of the fuzzing corpus changing
+depending on the random numbers. This also has an effect for coverage of the
+rest of the test suite and you see the coverage change for each commit even when
+no code has been modified.
+
+Since we want to maximize the coverage of the fuzzing corpus, the client and
+server fuzzer will use predictable numbers instead of the random numbers. This
+is controlled by the FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION define.
+
+The coverage depends on the way the numbers are generated. We don't disable any
+check of hashes, but the corpus has the correct hash in it for the random
+numbers that were generated. For instance the client fuzzer will always generate
+the same client hello with the same random number in it, and so the server, as
+emulated by the file, can be generated for that client hello.
+
+Coverage changes
+================
+
+Since the corpus depends on the default behaviour of the client and the server,
+changes in what they send by default will have an impact on the coverage. The
+corpus will need to be updated in that case.
+
+Updating the corpus
+===================
+
+The client and server corpus is generated with multiple config options:
+- The options as documented above
+- Without enable-ec_nistp_64_gcc_128 and without --debug
+- With no-asm
+- Using 32 bit
+- A default config, plus options needed to generate the fuzzer.
+
+The libfuzzer merge option is used to add the additional coverage
+from each config to the minimal set.