[PATCH net 7/7] selftests: tcp_ao: cover legacy and extended TCP_REPAIR_WINDOW layouts

Wesley Atwell
2026-03-11T07:56:42Z

Extend the repair helpers and selftests so the ABI contract is pinned
down in-tree.

The TCP-AO restore coverage now exercises both the exact and legacy
TCP_REPAIR_WINDOW layouts, verifies that intermediate lengths are
rejected, and keeps the packetdrill coverage for the advertised-window
receive-memory regressions in the same net selftest series.

Signed-off-by: Wesley Atwell <atwellwea@gmail.com>
---
.../net/packetdrill/tcp_rcv_toobig.pkt | 35 +++++++
.../packetdrill/tcp_rcv_toobig_default.pkt | 97 +++++++++++++++++++
.../testing/selftests/net/tcp_ao/lib/aolib.h | 56 +++++++++--
.../testing/selftests/net/tcp_ao/lib/repair.c | 18 ++--
.../selftests/net/tcp_ao/self-connect.c | 61 ++++++++++--
5 files changed, 244 insertions(+), 23 deletions(-)
create mode 100644 tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt
create mode 100644 tools/testing/selftests/net/packetdrill/tcp_rcv_toobig_default.pkt

diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt b/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt
new file mode 100644
index 000000000000..723c739ddc32
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+
+--mss=1000
+
+`./defaults.sh`
+
+ 0 `nstat -n`
+
+// Establish a connection.
+ +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+ +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+ +0 setsockopt(3, SOL_SOCKET, SO_RCVBUF, [20000], 4) = 0
+ +0 bind(3, ..., ...) = 0
+ +0 listen(3, 1) = 0
+
+ +0 < S 0:0(0) win 32792 <mss 1000,nop,wscale 7>
+ +0 > S. 0:0(0) ack 1 win 18980 <mss 1460,nop,wscale 0>
+ +.1 < . 1:1(0) ack 1 win 257
+
+ +0 accept(3, ..., ...) = 4
+
+ +0 < P. 1:20001(20000) ack 1 win 257
+ +.04 > . 1:1(0) ack 20001 win 18000
+
+ +0 setsockopt(4, SOL_SOCKET, SO_RCVBUF, [12000], 4) = 0
+ +0 < P. 20001:80001(60000) ack 1 win 257
+ +0 > . 1:1(0) ack 20001 win 18000
+
+ +0 read(4, ..., 20000) = 20000
+
+// A too big packet is accepted if the receive queue is empty, but the
+// stronger admission path must not zero the receive buffer while doing so.
+ +0 < P. 20001:80001(60000) ack 1 win 257
+ +0 > . 1:1(0) ack 80001 win 0
+ +0 %{ assert SK_MEMINFO_RCVBUF > 0, SK_MEMINFO_RCVBUF }%
diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig_default.pkt b/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig_default.pkt
new file mode 100644
index 000000000000..b2e4950e0b83
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig_default.pkt
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0
+
+--mss=1000
+
+`./defaults.sh
+sysctl -q net.ipv4.tcp_moderate_rcvbuf=0`
+
+// Establish a connection on the default receive buffer. Leave a large skb in
+// the queue, then deliver another one which still fits the remaining rwnd.
+// We should grow sk_rcvbuf to honor the already-advertised window instead of
+// dropping the packet.
+ +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+ +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+ +0 bind(3, ..., ...) = 0
+ +0 listen(3, 1) = 0
+
+ +0 < S 0:0(0) win 65535 <mss 1000,nop,nop,sackOK,nop,wscale 7>
+ +0 > S. 0:0(0) ack 1 <...>
+ +.1 < . 1:1(0) ack 1 win 257
+
+ +0 accept(3, ..., ...) = 4
+
+// Exchange enough data to get past the completely fresh-socket case while
+// still keeping the receive buffer at its 128kB default.
+ +0 < P. 1:65001(65000) ack 1 win 257
+ * > . 1:1(0) ack 65001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 65001:130001(65000) ack 1 win 257
+ * > . 1:1(0) ack 130001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 130001:195001(65000) ack 1 win 257
+ * > . 1:1(0) ack 195001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 195001:260001(65000) ack 1 win 257
+ * > . 1:1(0) ack 260001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 260001:325001(65000) ack 1 win 257
+ * > . 1:1(0) ack 325001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 325001:390001(65000) ack 1 win 257
+ * > . 1:1(0) ack 390001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 390001:455001(65000) ack 1 win 257
+ * > . 1:1(0) ack 455001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 455001:520001(65000) ack 1 win 257
+ * > . 1:1(0) ack 520001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 520001:585001(65000) ack 1 win 257
+ * > . 1:1(0) ack 585001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 585001:650001(65000) ack 1 win 257
+ * > . 1:1(0) ack 650001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 650001:715001(65000) ack 1 win 257
+ * > . 1:1(0) ack 715001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 715001:780001(65000) ack 1 win 257
+ * > . 1:1(0) ack 780001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 780001:845001(65000) ack 1 win 257
+ * > . 1:1(0) ack 845001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 845001:910001(65000) ack 1 win 257
+ * > . 1:1(0) ack 910001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 910001:975001(65000) ack 1 win 257
+ * > . 1:1(0) ack 975001
+ +0 read(4, ..., 65000) = 65000
+
+ +0 < P. 975001:1040001(65000) ack 1 win 257
+ * > . 1:1(0) ack 1040001
+ +0 read(4, ..., 65000) = 65000
+
+// Leave about 60kB queued, then accept another large skb which still fits
+// the rwnd we already exposed to the peer. The regression is the drop; the
+// exact sk_rcvbuf growth path is an implementation detail.
+ +0 < P. 1040001:1102001(62000) ack 1 win 257
+ * > . 1:1(0) ack 1102001
+
+ +0 < P. 1102001:1167001(65000) ack 1 win 257
+ * > . 1:1(0) ack 1167001
+ +0 read(4, ..., 127000) = 127000
diff --git a/tools/testing/selftests/net/tcp_ao/lib/aolib.h b/tools/testing/selftests/net/tcp_ao/lib/aolib.h
index ebb2899c12fe..ff259795a4a0 100644
--- a/tools/testing/selftests/net/tcp_ao/lib/aolib.h
+++ b/tools/testing/selftests/net/tcp_ao/lib/aolib.h
@@ -13,6 +13,7 @@
#include <linux/snmp.h>
#include <linux/tcp.h>
#include <netinet/in.h>
+#include <stddef.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdlib.h>
@@ -671,17 +672,42 @@ struct tcp_sock_state {
int timestamp;
};

-extern void __test_sock_checkpoint(int sk, struct tcp_sock_state *state,
- void *addr, size_t addr_size);
+/* Legacy userspace stops before the snapshot field and therefore exercises
+ * the kernel's unknown-snapshot fallback path.
+ */
+static inline socklen_t test_tcp_repair_window_legacy_size(void)
+{
+ return offsetof(struct tcp_repair_window, rcv_wnd_scaling_ratio);
+}
+
+static inline socklen_t test_tcp_repair_window_exact_size(void)
+{
+ return sizeof(struct tcp_repair_window);
+}
+
+void __test_sock_checkpoint_opt(int sk, struct tcp_sock_state *state,
+ socklen_t trw_len,
+ void *addr, size_t addr_size);
static inline void test_sock_checkpoint(int sk, struct tcp_sock_state *state,
sockaddr_af *saddr)
{
- __test_sock_checkpoint(sk, state, saddr, sizeof(*saddr));
+ __test_sock_checkpoint_opt(sk, state, test_tcp_repair_window_exact_size(),
+ saddr, sizeof(*saddr));
+}
+
+static inline void test_sock_checkpoint_legacy(int sk,
+ struct tcp_sock_state *state,
+ sockaddr_af *saddr)
+{
+ __test_sock_checkpoint_opt(sk, state, test_tcp_repair_window_legacy_size(),
+ saddr, sizeof(*saddr));
}
extern void test_ao_checkpoint(int sk, struct tcp_ao_repair *state);
-extern void __test_sock_restore(int sk, const char *device,
- struct tcp_sock_state *state,
- void *saddr, void *daddr, size_t addr_size);
+void __test_sock_restore_opt(int sk, const char *device,
+ struct tcp_sock_state *state,
+ socklen_t trw_len,
+ void *saddr, void *daddr,
+ size_t addr_size);
static inline void test_sock_restore(int sk, struct tcp_sock_state *state,
sockaddr_af *saddr,
const union tcp_addr daddr,
@@ -690,7 +716,23 @@ static inline void test_sock_restore(int sk, struct tcp_sock_state *state,
sockaddr_af addr;

tcp_addr_to_sockaddr_in(&addr, &daddr, htons(dport));
- __test_sock_restore(sk, veth_name, state, saddr, &addr, sizeof(addr));
+ __test_sock_restore_opt(sk, veth_name, state,
+ test_tcp_repair_window_exact_size(),
+ saddr, &addr, sizeof(addr));
+}
+
+static inline void test_sock_restore_legacy(int sk,
+ struct tcp_sock_state *state,
+ sockaddr_af *saddr,
+ const union tcp_addr daddr,
+ unsigned int dport)
+{
+ sockaddr_af addr;
+
+ tcp_addr_to_sockaddr_in(&addr, &daddr, htons(dport));
+ __test_sock_restore_opt(sk, veth_name, state,
+ test_tcp_repair_window_legacy_size(),
+ saddr, &addr, sizeof(addr));
}
extern void test_ao_restore(int sk, struct tcp_ao_repair *state);
extern void test_sock_state_free(struct tcp_sock_state *state);
diff --git a/tools/testing/selftests/net/tcp_ao/lib/repair.c b/tools/testing/selftests/net/tcp_ao/lib/repair.c
index 9893b3ba69f5..befbd0f72db5 100644
--- a/tools/testing/selftests/net/tcp_ao/lib/repair.c
+++ b/tools/testing/selftests/net/tcp_ao/lib/repair.c
@@ -66,8 +66,9 @@ static void test_sock_checkpoint_queue(int sk, int queue, int qlen,
test_error("recv(%d): %d", qlen, ret);
}

-void __test_sock_checkpoint(int sk, struct tcp_sock_state *state,
- void *addr, size_t addr_size)
+void __test_sock_checkpoint_opt(int sk, struct tcp_sock_state *state,
+ socklen_t trw_len,
+ void *addr, size_t addr_size)
{
socklen_t len = sizeof(state->info);
int ret;
@@ -82,9 +83,9 @@ void __test_sock_checkpoint(int sk, struct tcp_sock_state *state,
if (getsockname(sk, addr, &len) || len != addr_size)
test_error("getsockname(): %d", (int)len);

- len = sizeof(state->trw);
+ len = trw_len;
ret = getsockopt(sk, SOL_TCP, TCP_REPAIR_WINDOW, &state->trw, &len);
- if (ret || len != sizeof(state->trw))
+ if (ret || len != trw_len)
test_error("getsockopt(TCP_REPAIR_WINDOW): %d", (int)len);

if (ioctl(sk, SIOCOUTQ, &state->outq_len))
@@ -160,9 +161,10 @@ static void test_sock_restore_queue(int sk, int queue, void *buf, int len)
} while (len > 0);
}

-void __test_sock_restore(int sk, const char *device,
- struct tcp_sock_state *state,
- void *saddr, void *daddr, size_t addr_size)
+void __test_sock_restore_opt(int sk, const char *device,
+ struct tcp_sock_state *state,
+ socklen_t trw_len,
+ void *saddr, void *daddr, size_t addr_size)
{
struct tcp_repair_opt opts[4];
unsigned int opt_nr = 0;
@@ -215,7 +217,7 @@ void __test_sock_restore(int sk, const char *device,
}
test_sock_restore_queue(sk, TCP_RECV_QUEUE, state->in.buf, state->inq_len);
test_sock_restore_queue(sk, TCP_SEND_QUEUE, state->out.buf, state->outq_len);
- if (setsockopt(sk, SOL_TCP, TCP_REPAIR_WINDOW, &state->trw, sizeof(state->trw)))
+ if (setsockopt(sk, SOL_TCP, TCP_REPAIR_WINDOW, &state->trw, trw_len))
test_error("setsockopt(TCP_REPAIR_WINDOW)");
}

diff --git a/tools/testing/selftests/net/tcp_ao/self-connect.c b/tools/testing/selftests/net/tcp_ao/self-connect.c
index 2c73bea698a6..a7edd72ab28d 100644
--- a/tools/testing/selftests/net/tcp_ao/self-connect.c
+++ b/tools/testing/selftests/net/tcp_ao/self-connect.c
@@ -4,6 +4,7 @@
#include "aolib.h"

static union tcp_addr local_addr;
+static bool checked_repair_window_lens;

static void __setup_lo_intf(const char *lo_intf,
const char *addr_str, uint8_t prefix)
@@ -30,8 +31,40 @@ static void setup_lo_intf(const char *lo_intf)
#endif
}

+/* The repair ABI accepts exactly the legacy and extended layouts. */
+static void test_repair_window_len_contract(int sk)
+{
+ struct tcp_repair_window trw = {};
+ socklen_t len = test_tcp_repair_window_exact_size();
+ socklen_t bad_len = test_tcp_repair_window_legacy_size() + 1;
+ int ret;
+
+ if (checked_repair_window_lens)
+ return;
+
+ checked_repair_window_lens = true;
+
+ ret = getsockopt(sk, SOL_TCP, TCP_REPAIR_WINDOW, &trw, &len);
+ if (ret || len != test_tcp_repair_window_exact_size())
+ test_error("getsockopt(TCP_REPAIR_WINDOW): %d", (int)len);
+
+ len = bad_len;
+ ret = getsockopt(sk, SOL_TCP, TCP_REPAIR_WINDOW, &trw, &len);
+ if (ret == 0 || errno != EINVAL)
+ test_fail("repair-window get rejects invalid len");
+ else
+ test_ok("repair-window get rejects invalid len");
+
+ ret = setsockopt(sk, SOL_TCP, TCP_REPAIR_WINDOW, &trw, bad_len);
+ if (ret == 0 || errno != EINVAL)
+ test_fail("repair-window set rejects invalid len");
+ else
+ test_ok("repair-window set rejects invalid len");
+}
+
static void tcp_self_connect(const char *tst, unsigned int port,
- bool different_keyids, bool check_restore)
+ bool different_keyids, bool check_restore,
+ bool legacy_repair_window)
{
struct tcp_counters before, after;
uint64_t before_aogood, after_aogood;
@@ -109,7 +142,11 @@ static void tcp_self_connect(const char *tst, unsigned int port,
}

test_enable_repair(sk);
- test_sock_checkpoint(sk, &img, &addr);
+ test_repair_window_len_contract(sk);
+ if (legacy_repair_window)
+ test_sock_checkpoint_legacy(sk, &img, &addr);
+ else
+ test_sock_checkpoint(sk, &img, &addr);
#ifdef IPV6_TEST
addr.sin6_port = htons(port + 1);
#else
@@ -123,7 +160,11 @@ static void tcp_self_connect(const char *tst, unsigned int port,
test_error("socket()");

test_enable_repair(sk);
- __test_sock_restore(sk, "lo", &img, &addr, &addr, sizeof(addr));
+ __test_sock_restore_opt(sk, "lo", &img,
+ legacy_repair_window ?
+ test_tcp_repair_window_legacy_size() :
+ test_tcp_repair_window_exact_size(),
+ &addr, &addr, sizeof(addr));
if (different_keyids) {
if (test_add_repaired_key(sk, DEFAULT_TEST_PASSWORD, 0,
local_addr, -1, 7, 5))
@@ -165,20 +206,24 @@ static void *client_fn(void *arg)

setup_lo_intf("lo");

- tcp_self_connect("self-connect(same keyids)", port++, false, false);
+ tcp_self_connect("self-connect(same keyids)", port++, false, false, false);

/* expecting rnext to change based on the first segment RNext != Current */
trace_ao_event_expect(TCP_AO_RNEXT_REQUEST, local_addr, local_addr,
port, port, 0, -1, -1, -1, -1, -1, 7, 5, -1);
- tcp_self_connect("self-connect(different keyids)", port++, true, false);
- tcp_self_connect("self-connect(restore)", port, false, true);
+ tcp_self_connect("self-connect(different keyids)", port++, true, false, false);
+ tcp_self_connect("self-connect(restore)", port, false, true, false);
+ port += 2; /* restore test restores over different port */
+ tcp_self_connect("self-connect(restore, legacy repair window)",
+ port, false, true, true);
port += 2; /* restore test restores over different port */
trace_ao_event_expect(TCP_AO_RNEXT_REQUEST, local_addr, local_addr,
port, port, 0, -1, -1, -1, -1, -1, 7, 5, -1);
/* intentionally on restore they are added to the socket in different order */
trace_ao_event_expect(TCP_AO_RNEXT_REQUEST, local_addr, local_addr,
port + 1, port + 1, 0, -1, -1, -1, -1, -1, 5, 7, -1);
- tcp_self_connect("self-connect(restore, different keyids)", port, true, true);
+ tcp_self_connect("self-connect(restore, different keyids)",
+ port, true, true, false);
port += 2; /* restore test restores over different port */

return NULL;
@@ -186,6 +231,6 @@ static void *client_fn(void *arg)

int main(int argc, char *argv[])
{
- test_init(5, client_fn, NULL);
+ test_init(8, client_fn, NULL);
return 0;
}
--
2.34.1