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Date: Mon, 20 Apr 2015 22:26:18 +0300
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: Mark Johnston <markj@FreeBSD.org>
Cc: freebsd-net@FreeBSD.org
Subject: Re: moving struct bpf_if to bpf.c
Message-ID: <20150420192618.GY883@FreeBSD.org>
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On Sat, Apr 18, 2015 at 02:08:56PM -0700, Mark Johnston wrote:
M> At the moment, bpf.h defines struct bpf_if differently depending on
M> whether BPF_INTERNAL is #defined. This causes problems with CTF, as it
M> results in a sort of bifurcation within the type graph: CTF sees two
M> different struct bpf_ifs, and so every struct/union containing a struct
M> bpf_if is duplicated, and so on. CTF currently imposes a limit of 2^15
M> distinct types within a container, and several people have been running
M> into this limit. The type duplication exacerbates this problem.
M> 
M> The change here fixes the issue by moving the definition of
M> struct bpf_if to bpf.c, and making its externally-used fields
M> available via struct bpf_if_ext: https://reviews.freebsd.org/D2319
M> 
M> In particular, the ext fields are at the same offsets within struct
M> bpf_if as before, so this change should have no functional impact.
M> Moreover, it reduces the number of types from 20879 to 15725 with my
M> (stripped-down) kernel config on amd64. Would anyone be willing to
M> review the proposed change? I've also placed the raw diff here:
M> https://people.freebsd.org/~markj/patches/bpf_entrails.diff

What actual software needs to look at struct bpf_if? I wonder if
we can fix the software and hide the struct bpf_if into kernel
entirely.

-- 
Totus tuus, Glebius.