Open Source Computing

Week 12 (4/12)

No class 4/10

Some open-source projects and how they handle:

Many of these are from


This is a kind of remote browser. It might not display the full rendered content of the page, but you can use it to make remote browser GET/POST requests, and get the results. Results by default are downloaded to the remote server, but it is straightforward to fetch them from there; security-scanning is recommended. (Note the "WTF is this?" section, which was added a week or so after the project first went up (the readme continues to expand rapidly).)

The monetizing-open-source model here mostly seems to be that the open version is a trial version. It's not time-limited, but nor is it quite open-core.

Things to look at:

What do you think of that license?

The Polyform Project

The argument here is that these are just various "source-available" licenses. They do state outright that "Polyform is not ... Open source or free software."

Licenses to look at:

They give a list of related licenses: an add-on license (to any "permissive" open-source license) that restricts sale, but still allows forking.

Elastic license ( note the "Copyright" and "Limitations" sections. You do get to fork the original project, subject to the Limitations, which here are relatively substantial. Can you rewrite the portions of code covered by the license key, so the functionality is available without a license? Looks that way to me, though that might be a big project.

Confluent license ( Note the Developer (no time limit, but "single-broker") and Trial (30-day) licenses. No copyright rights are extended by the license.


A python plotting library

Has Also, for users


Lower down, there is a "contributing to plotly" link and a "Community forum" link.


Most recent update is 5 years ago; most are 9+ years ago

Project Abandoned


An astrophysics library for Python

Has a contributions page at

At there is quite a discussion about the project organization. There is a very long list of contributors, and a list of around ~45 voting members.

Linux kernel source

Brief overview of TCP

Start with af_inet.c::tcp_protocol() and tcp_ipv4::tcp_v4_rcv
    => __inet_lookup_skb => __inet_lookup()
    => tcp_v4_do_rcv
        =>     tcp_rcv_established() | tcp_v4_hnd_req(sk, skb) | tcp_child_process
        =>     tcp_input.c::tcp_rcv_state_process()
                    -> icsk->icsk_af_ops->conn_request(sk, skb)
        == tcp_v4_conn_request()        // see table at tcp_ipv4.c::line 1758

    inet_csk_search_req: this is looking for the "request socket", a mini-socket with additional info
    tcp_check_req: checks if there is space in the accept queue
    inet_lookup_established: we *did* just call this: same as __inet_lookup_established with hnum=dport
    main path: ends up returning sk

Caller is tcp_v4_do_rcv();
    caller falls through to tcp_rcv_state_process
        -> icsk->icsk_af_ops->conn_request(sk, skb)
        == tcp_v4_conn_request()        // see table at tcp_ipv4.c::line 1758

tcp_v4_conn_request():        // handles incoming SYN
    // error cases first
    save saddr/daddr in ireq, which is a cast of req, which is a struct request_sock.

    saves req using inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);    // csk = Connected SocKet
    see also inet_csk_search_req
    calls __tcp_v4_send_synack

    int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)    // called by tcp_v4_do_rcv for states besides ESTABLISHED, LISTEN
    ESTABLISHED: tcp_data_queue()

Brief overview of HTB