[PATCH bpf] bpf, sockmap: Account for receive queue in FIONREAD without a verdict program
From: Mattia Meleleo via B4 Relay <devnull+mattia.meleleo.coralogix.com@kernel.org>
Date: 2026-07-07 16:16:03
Also in:
b4-sent, bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [l7 framework] (sockmap), bpf [selftests] (test runners & infrastructure), kernel selftest framework, networking [general], networking [tcp], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, John Fastabend, Jakub Sitnicki, Jiayuan Chen, Shuah Khan, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Mattia Meleleo <redacted>
tcp_bpf_ioctl() answers SIOCINQ from psock->msg_tot_len, which only
counts bytes in ingress_msg. Without a stream/skb verdict program
nothing is diverted there: data stays in sk_receive_queue, so FIONREAD
returns 0 even though read() returns data.
Add tcp_inq() to the reported value when the psock has no verdict
program. The two queues are disjoint, so bytes redirected into
ingress_msg from other sockets stay correctly accounted through
msg_tot_len.
Add a selftest covering FIONREAD without a verdict program.
Fixes: 929e30f93125 ("bpf, sockmap: Fix FIONREAD for sockmap")
Signed-off-by: Mattia Meleleo <redacted>
---
net/ipv4/tcp_bpf.c | 16 ++++++++-
.../selftests/bpf/prog_tests/sockmap_basic.c | 39 ++++++++++++++++++++++
2 files changed, 54 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index cc0bd73f3..a001b1fff 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c@@ -334,6 +334,7 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk, static int tcp_bpf_ioctl(struct sock *sk, int cmd, int *karg) { + struct sk_psock *psock; bool slow; if (cmd != SIOCINQ)
@@ -344,7 +345,20 @@ static int tcp_bpf_ioctl(struct sock *sk, int cmd, int *karg) return -EINVAL; slow = lock_sock_fast(sk); - *karg = sk_psock_msg_inq(sk); + psock = sk_psock_get(sk); + if (unlikely(!psock)) { + unlock_sock_fast(sk, slow); + return tcp_ioctl(sk, cmd, karg); + } + *karg = sk_psock_get_msg_len_nolock(psock); + /* Without a verdict program, ingress data is never diverted to + * ingress_msg: it stays in sk_receive_queue and is read through + * the fallback to tcp_recvmsg(), so account for it like + * tcp_ioctl() does. + */ + if (!psock->progs.stream_verdict && !psock->progs.skb_verdict) + *karg += tcp_inq(sk); + sk_psock_put(sk, psock); unlock_sock_fast(sk, slow); return 0;
diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
index cb3229711..f0f368201 100644
--- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c@@ -1373,6 +1373,43 @@ static void test_sockmap_multi_channels(int sotype) test_sockmap_pass_prog__destroy(skel); } +/* A socket in a sockmap without a verdict program keeps its ingress data + * in sk_receive_queue: FIONREAD must account for it. + */ +static void test_sockmap_no_verdict_fionread(void) +{ + int err, map, zero = 0, sent, avail; + int c0 = -1, c1 = -1, p0 = -1, p1 = -1; + struct test_sockmap_pass_prog *skel; + char buf[256] = "0123456789"; + + skel = test_sockmap_pass_prog__open_and_load(); + if (!ASSERT_OK_PTR(skel, "open_and_load")) + return; + map = bpf_map__fd(skel->maps.sock_map_rx); + + err = create_socket_pairs(AF_INET, SOCK_STREAM, &c0, &c1, &p0, &p1); + if (!ASSERT_OK(err, "create_socket_pairs()")) + goto out; + + err = bpf_map_update_elem(map, &zero, &c1, BPF_NOEXIST); + if (!ASSERT_OK(err, "bpf_map_update_elem(c1)")) + goto out_close; + + sent = xsend(p1, &buf, sizeof(buf), 0); + ASSERT_EQ(sent, sizeof(buf), "xsend(p1)"); + avail = wait_for_fionread(c1, sizeof(buf), IO_TIMEOUT_SEC); + ASSERT_EQ(avail, sizeof(buf), "ioctl(FIONREAD)"); + +out_close: + close(c0); + close(p0); + close(c1); + close(p1); +out: + test_sockmap_pass_prog__destroy(skel); +} + void test_sockmap_basic(void) { if (test__start_subtest("sockmap create_update_free"))
@@ -1415,6 +1452,8 @@ void test_sockmap_basic(void) test_sockmap_skb_verdict_shutdown(); if (test__start_subtest("sockmap skb_verdict fionread")) test_sockmap_skb_verdict_fionread(true); + if (test__start_subtest("sockmap no_verdict fionread")) + test_sockmap_no_verdict_fionread(); if (test__start_subtest("sockmap skb_verdict fionread on drop")) test_sockmap_skb_verdict_fionread(false); if (test__start_subtest("sockmap skb_verdict change tail"))
--- base-commit: d2c9a99135da931377240942d44f3dea104cedb8 change-id: 20260707-fionread-no-verdict-a4f8697ac9f9 Best regards, -- Mattia Meleleo [off-list ref]