Re: [PATCH net 2/2] selftests: tls: add a test for splicing onto a full plaintext record

[Sabrina Dubroca <sd@queasysnail.net>]

2026-07-26, 19:55:56 +0900, chanyoung wrote:
> diff --git a/tools/testing/selftests/net/tls.c b/tools/testing/selftests/net/tls.c
> index cbdd3ea28b9..d2666884ea8 100644
> --- a/tools/testing/selftests/net/tls.c
> +++ b/tools/testing/selftests/net/tls.c
> @@ -835,6 +835,58 @@ TEST_F(tls, send_and_splice)
>  	EXPECT_EQ(memcmp(mem_send, mem_recv, send_len), 0);
>  }
>  
> +/* Splicing into an open record whose plaintext scatterlist ring is already
> + * full used to wrap the ring's end index onto its start, after which
> + * sk_msg_full() reported the full ring as empty: further pages overwrote
> + * live entries and sg.size desynced from the walkable scatterlist, which
> + * oopsed in the AEAD walk once the record was pushed.  The ring is left
> + * full and unpushed by the copy path, which does not push the record when
> + * the fragment it adds is the one that fills the ring.
> + */

This comment (and the other one above the loop) duplicates contents of
the commit message. Please drop them.

> +TEST_F(tls, splice_onto_full_record)
> +{
> +	int frag_len = 100, extra = 4;

Why 4 extra splices? One should be enough to hit tls_sw_sendmsg_splice
with the skmsg already full?

> +	char mem_send[5000];
> +	char mem_recv[5000];
> +	int nfrags, i, total;
> +	int p[2];
> +
> +	memrnd(mem_send, sizeof(mem_send));
> +
> +	/* MAX_SKB_FRAGS is configurable (17 by default), so sweep the
> +	 * plausible range to land the one-byte send exactly on a full ring
> +	 * whatever this kernel was built with.
> +	 */
> +	for (nfrags = 12; nfrags <= 45; nfrags++) {
> +		total = (nfrags + extra) * frag_len + 2;
> +
> +		for (i = 0; i < nfrags; i++) {
> +			ASSERT_GE(pipe(p), 0);

Do we really need a fresh pipe for each iteration?

> +			EXPECT_EQ(write(p[1], mem_send, frag_len), frag_len);
> +			EXPECT_EQ(splice(p[0], NULL, self->fd, NULL, frag_len,
> +					 SPLICE_F_MORE), frag_len);
> +			close(p[0]);
> +			close(p[1]);
> +		}
> +
> +		EXPECT_EQ(send(self->fd, mem_send, 1, MSG_MORE), 1);
> +
> +		for (i = 0; i < extra; i++) {
> +			ASSERT_GE(pipe(p), 0);
> +			EXPECT_EQ(write(p[1], mem_send, frag_len), frag_len);
> +			EXPECT_EQ(splice(p[0], NULL, self->fd, NULL, frag_len,
> +					 SPLICE_F_MORE), frag_len);
> +			close(p[0]);
> +			close(p[1]);
> +		}
> +
> +		EXPECT_EQ(send(self->fd, mem_send, 1, 0), 1);
> +
> +		EXPECT_EQ(recv(self->cfd, mem_recv, total, MSG_WAITALL), total);
> +		EXPECT_EQ(memcmp(mem_send, mem_recv, frag_len), 0);

Only comparing the first chunk ("frag_len" bytes) and not the full blob
("total" bytes) isn't very useful.

> +	}
> +}
> +
>  TEST_F(tls, splice_to_pipe)
>  {
>  	int send_len = TLS_PAYLOAD_MAX_LEN;
> -- 
> 2.43.0
> 

-- 
Sabrina