Re: [PATCH net v3 3/3] selftests: net: add TAP socket filter attach tests

[Rongguang Wei <clementwei90@163.com>]

on 2026/10/1 03:20, Willem de Bruijn wrote:
> Rongguang Wei wrote:
>> From: Rongguang Wei <weirongguang@kylinos.cn>
>>
>> reattach_filter_without_user_buffer() attaches a filter, makes the buffer
>> the program was copied from unreadable and then attaches the queue again,
>> which used to fail with -EFAULT.
>>
>> attach_filter_bad_len_keeps_program() checks that a rejected
>> TUNATTACHFILTER leaves both the saved program and the installed filter
>> alone.
>>
>> attach_filter_nofilter_flag() and detach_filter_clears_reattach() cover the
>> ways to attach a queue without a filter.
>>
>> Signed-off-by: Rongguang Wei <weirongguang@kylinos.cn>
> 
> Reviewed-by: Willem de Bruijn <willemb@google.com>
> 
> 
>> +TEST_F(tun, reattach_filter_without_user_buffer)
>> +{
>> +	struct sock_fprog gf = { 0 };
>> +	short flags = 0;
>> +	void *prog;
>> +	int ret;
>> +
>> +	prog = filter_alloc(filter_accept, ARRAY_SIZE(filter_accept));
>> +	ASSERT_NE(prog, NULL);
>> +	ASSERT_EQ(filter_attach(self->fd, prog, ARRAY_SIZE(filter_accept)), 0);
>> +
>> +	EXPECT_EQ(tun_detach(self->fd, self->ifname), 0);
>> +
>> +	/* The process that called TUNATTACHFILTER no longer maps this memory */
>> +	ASSERT_EQ(mprotect(prog, getpagesize(), PROT_NONE), 0);
>> +
>> +	ret = tun_attach(self->fd, self->ifname);
>> +	EXPECT_EQ(ret, 0);
>> +
>> +	flags = tun_get_iff_flags(self->fd);
>> +	EXPECT_GE(flags, 0);
>> +	EXPECT_EQ(flags & IFF_NOFILTER, 0);
> 
> iff a respin is needed, consider adding the extra test to make sure that
> tun_attach did not just succeed without attaching the program, as it does
> before patch 2.
> 
> EXPECT_EQ(flags & IFF_DETACH_QUEUE, 0);
> 
Yes, I will add it in V4. Thank you.
>> +
>> +	EXPECT_EQ(filter_get(self->fd, &gf), 0);
>> +	EXPECT_EQ(gf.len, ARRAY_SIZE(filter_accept));
>> +
>> +	ASSERT_EQ(mprotect(prog, getpagesize(), PROT_READ | PROT_WRITE), 0);
>> +	ASSERT_EQ(munmap(prog, getpagesize()), 0);
>> +}