To build Neqo:

cargo build

This will use a system-installed NSS library if it is new enough. (See "Build with Separate NSS/NSPR" below if NSS is not installed or it is deemed too old.)

To run test HTTP/3 programs (neqo-client and neqo-server):

./target/debug/neqo-server '[::]:12345'
./target/debug/neqo-client 'https://[::]:12345/'

You can clone NSS and NSPR into the same directory and export an environment variable called NSS_DIR pointing to NSS. This causes the build to use the existing NSS checkout. However, in order to run anything that depends on NSS, you need to set an environment as follows:

export LD_LIBRARY_PATH="$(dirname "$(find . -name libssl3.so -print | head -1)")"

export DYLD_LIBRARY_PATH="$(dirname "$(find . -name libssl3.dylib -print | head -1)")"

Note: If you did not already compile NSS separately, you need to have Mercurial (hg), installed. NSS builds require GYP and Ninja to be installed.

Enable generation of QLOG logs with:

target/debug/neqo-server '[::]:12345' --qlog-dir .
target/debug/neqo-client 'https://[::]:12345/' --qlog-dir .

You can of course specify a different directory for the QLOG files. You can upload QLOG files to qvis to visualize the flows.

You can export TLS keys by setting the SSLKEYLOGFILE environment variable to a filename to instruct NSS to dump keys in the standard format to enable decryption by Wireshark and other tools.

As documented in the env_logger documentation, the RUST_LOG environment variable can be used to selectively enable log messages from Rust code. This works for Neqo's command line tools, as well as for when Neqo is incorporated into Gecko, although Gecko needs to be built in debug mode.

Some examples:

1. RUST_LOG=neqo_transport::dump ./mach run

   lists sent and received QUIC packets and their frames' contents only.

2. RUST_LOG=neqo_transport=debug,neqo_http3=trace,info ./mach run

   sets a debug log level for transport, trace level for http3, and info log level for all other Rust crates, both Neqo and others used by Gecko.

3. RUST_LOG=neqo=trace,error ./mach run

   sets trace level for all modules starting with neqo, and sets error as minimum log level for other unrelated Rust log messages.

In a checked-out copy of Gecko source, set [patches.*] values for the four Neqo crates to local versions in the root Cargo.toml. For example, if Neqo was checked out to /home/alice/git/neqo, add the following lines to the root Cargo.toml.

[patch."https://github.com/mozilla/neqo"]
neqo-http3 = { path = "/home/alice/git/neqo/neqo-http3" }
neqo-transport = { path = "/home/alice/git/neqo/neqo-transport" }
neqo-common = { path = "/home/alice/git/neqo/neqo-common" }
neqo-qpack = { path = "/home/alice/git/neqo/neqo-qpack" }
neqo-crypto = { path = "/home/alice/git/neqo/neqo-crypto" }

Then run the following:

./mach vendor rust

Compile Gecko as usual with

./mach build

Note: Using newer Neqo code with Gecko may also require changes (likely to neqo_glue) if something has changed.