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Date:   Wed, 6 Jan 2021 13:39:46 -0800
From:   Martin KaFai Lau <kafai@fb.com>
To:     Alan Maguire <alan.maguire@oracle.com>
CC:     <ast@kernel.org>, <daniel@iogearbox.net>, <andrii@kernel.org>,
        <songliubraving@fb.com>, <yhs@fb.com>, <john.fastabend@gmail.com>,
        <kpsingh@kernel.org>, <toke@redhat.com>, <wanghai38@huawei.com>,
        <quentin@isovalent.com>, <netdev@vger.kernel.org>,
        <bpf@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf] bpftool: fix compilation failure for net.o with
 older glibc
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On Wed, Jan 06, 2021 at 03:59:06PM +0000, Alan Maguire wrote:
> For older glibc ~2.17, #include'ing both linux/if.h and net/if.h
> fails due to complaints about redefinition of interface flags:
> 
>   CC       net.o
> In file included from net.c:13:0:
> /usr/include/linux/if.h:71:2: error: redeclaration of enumerator ‘IFF_UP’
>   IFF_UP    = 1<<0,  /* sysfs */
>   ^
> /usr/include/net/if.h:44:5: note: previous definition of ‘IFF_UP’ was here
>      IFF_UP = 0x1,  /* Interface is up.  */
> 
> The issue was fixed in kernel headers in [1], but since compilation
> of net.c picks up system headers the problem can recur.
> 
> Dropping #include <linux/if.h> resolves the issue and it is
> not needed for compilation anyhow.
Acked-by: Martin KaFai Lau <kafai@fb.com>