Date: Fri, 7 Oct 2016 07:34:27 -0400 From: Jonathan Looney <jonlooney@gmail.com> To: Adrian Chadd <adrian.chadd@gmail.com> Cc: "<freebsd-transport@freebsd.org>" <freebsd-transport@freebsd.org> Subject: Re: Remove (struct tcpcb) from the API? Message-ID: <CADrOrmsYa-JxBVA=yEOrXo%2B1XxVzxF%2BMi1L--kadTgGrH4x1Rw@mail.gmail.com> In-Reply-To: <CAJ-VmokX%2BW=F-KNOwCPHm=9-Lp1JzQKS%2BUJo7N-dEEnH2z1sug@mail.gmail.com> References: <CADrOrmuG_GvqnenU8g9UXGN3uPDyMOapHm%2BX85iNa-RNHp1wUQ@mail.gmail.com> <CAJ-VmokX%2BW=F-KNOwCPHm=9-Lp1JzQKS%2BUJo7N-dEEnH2z1sug@mail.gmail.com>
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On Thu, Oct 6, 2016 at 4:21 PM, Adrian Chadd <adrian.chadd@gmail.com> wrote:
> Wait, I thought we had xtcpcb or something to face userland?
>
Yes, but the xtcpcb structure includes the entire (struct tcpcb):
struct xtcpcb {
size_t xt_len;
struct inpcb xt_inp;
struct tcpcb xt_tp;
struct xsocket xt_socket;
struct xtcp_timer xt_timer;
u_quad_t xt_alignment_hack;
};
And, in tcp_pcblist():
struct xtcpcb xt;
[...]
inp_ppcb = inp->inp_ppcb;
[...]
bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
So, my proposal is to replace xt_tp with a minimal structure that includes
the (20 or so?) fields that userland actually cares about. Importantly, we
can then leave that structure as the stable API, while we are free to
modify the actual (struct tcpcb). Relatedly, this could cut down
substantially on the number of bytes we copy out for each TCP session
(which can really add up on a loaded box, and only adds to the overhead of
the locking).
Jonathan
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