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Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Shuah Khan , Willem de Bruijn , Wei Wang , Shakeel Butt , netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Octavian Purdila Content-Type: text/plain; charset="UTF-8" Add a packetdrill test that drives sk->sk_forward_alloc negative via tcp_collapse() on the receive queue while sk->sk_wmem_queued exceeds sysctl_tcp_wmem[0], and verifies that a subsequent non-blocking write() under TCP memory pressure fails with EAGAIN rather than returning a negative copy length from tcp_wmem_schedule() and failing with EFAULT. Assisted-by: LLM Signed-off-by: Octavian Purdila Reviewed-by: Kuniyuki Iwashima Signed-off-by: Octavian Purdila --- .../testing/selftests/net/packetdrill/config | 2 + .../selftests/net/packetdrill/ksft_runner.sh | 6 + .../tcp_wmem_schedule_negative_fwd_alloc.pkt | 108 ++++++++++++++++++ 3 files changed, 116 insertions(+) create mode 100644 tools/testing/selftests/net/packetdrill/tcp_wmem_schedule_negative_fwd_alloc.pkt diff --git a/tools/testing/selftests/net/packetdrill/config b/tools/testing/selftests/net/packetdrill/config index b7df8bf309200..a14a704dcbd49 100644 --- a/tools/testing/selftests/net/packetdrill/config +++ b/tools/testing/selftests/net/packetdrill/config @@ -1,6 +1,8 @@ +CONFIG_CGROUPS=y CONFIG_HZ=1000 CONFIG_HZ_1000=y CONFIG_IPV6=y +CONFIG_MEMCG=y CONFIG_NET_NS=y CONFIG_NET_SCH_FIFO=y CONFIG_NET_SCH_FQ=y diff --git a/tools/testing/selftests/net/packetdrill/ksft_runner.sh b/tools/testing/selftests/net/packetdrill/ksft_runner.sh index 0a97d5ae34699..dcda2b93c76e0 100755 --- a/tools/testing/selftests/net/packetdrill/ksft_runner.sh +++ b/tools/testing/selftests/net/packetdrill/ksft_runner.sh @@ -52,6 +52,12 @@ if [[ -n "${KSFT_MACHINE_SLOW}" ]]; then failfunc=ktap_test_xfail fi +pagesize=$(grep -E '^--define=REQUIRES_PAGESIZE=' $script | cut -d '=' -f 3 | tr -d '"') +if [[ -n "$pagesize" && "$(getconf PAGESIZE)" != "$pagesize" ]]; then + ktap_skip_all "requires ${pagesize}B PAGE_SIZE" + exit "$KSFT_SKIP" +fi + ip_versions=$(grep -E '^--ip_version=' $script | cut -d '=' -f 2) if [[ -z $ip_versions ]]; then ip_versions="ipv4 ipv6 ipv4-mapped-ipv6" diff --git a/tools/testing/selftests/net/packetdrill/tcp_wmem_schedule_negative_fwd_alloc.pkt b/tools/testing/selftests/net/packetdrill/tcp_wmem_schedule_negative_fwd_alloc.pkt new file mode 100644 index 0000000000000..f8b7386fe77e2 --- /dev/null +++ b/tools/testing/selftests/net/packetdrill/tcp_wmem_schedule_negative_fwd_alloc.pkt @@ -0,0 +1,108 @@ +// SPDX-License-Identifier: GPL-2.0 +// Test that tcp_wmem_schedule() clamps negative sk->sk_forward_alloc to 0 +// when sk_wmem_schedule() fails under memory pressure and +// sk->sk_wmem_queued >= sysctl_tcp_wmem[0], returning EAGAIN rather than EFAULT. +// +// Buffer and segment sizes are tuned for 4 KB pages and standard +// CONFIG_MAX_SKB_FRAGS values (17 to 45). + +--define=REQUIRES_PAGESIZE="4096" +--mtu=65535 +--tolerance_usecs=100000 + +`set -e +./defaults.sh +ip link set dev tun0 mtu 65535 +sysctl -q net.ipv4.tcp_rmem="4096 131072 6291456" +sysctl -q net.ipv4.tcp_wmem="4096 16384 4194304" +cgroot=$(mount -t cgroup2 | head -1 | awk '{print $3}') +[ -n "$cgroot" ] +echo +memory > "${cgroot}/cgroup.subtree_control" +rmdir "${cgroot}/pkt_${PPID}" 2>/dev/null || true +mkdir "${cgroot}/pkt_${PPID}" +echo $PPID > "${cgroot}/pkt_${PPID}/cgroup.procs" +` + +// Create listening socket in pkt_${PPID} memcg and establish connection +0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 ++0.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 ++0.000 bind(3, ..., ...) = 0 ++0.000 listen(3, 1) = 0 + ++0.000 < S 0:0(0) win 65535 ++0.000 > S. 0:0(0) ack 1 <...> ++0.000 < . 1:1(0) ack 1 win 512 ++0.000 accept(3, ..., ...) = 4 + +// Move packetdrill back to its original cgroup so subsequent packetdrill allocations are not charged to pkt_${PPID} ++0.000 `cgroot=$(mount -t cgroup2 | head -1 | awk '{print $3}') +runner_pid=$(awk '/^PPid:/ {print $2}' /proc/$PPID/status) +orig_cg=$(sed -n 's/^0:://p' /proc/$runner_pid/cgroup) +echo $PPID > "${cgroot}${orig_cg}/cgroup.procs"` + ++0.000 setsockopt(4, SOL_SOCKET, SO_SNDBUF, [200000], 4) = 0 ++0.000 setsockopt(4, SOL_SOCKET, SO_RCVBUF, [112500], 4) = 0 + +// 1. Warm up rcv_ssthresh to full window ++0.000 < P. 1:35001(35000) ack 1 win 512 ++0.000 > . 1:1(0) ack 35001 ++0.000 read(4, ..., 35000) = 35000 + ++0.000 < P. 35001:70001(35000) ack 1 win 512 ++0.000 > . 1:1(0) ack 70001 ++0.000 read(4, ..., 35000) = 35000 + ++0.000 < P. 70001:105001(35000) ack 1 win 512 ++0.000 > . 1:1(0) ack 105001 ++0.000 read(4, ..., 35000) = 35000 + ++0.000 < P. 105001:140001(35000) ack 1 win 512 ++0.000 > . 1:1(0) ack 140001 ++0.000 read(4, ..., 35000) = 35000 + +// 2. Queue 79 KB on TX so sk_wmem_queued >= sysctl_tcp_wmem[0], while leaving +// both tail SKB space (26 KB) and sk_page_frag space (19.3 KB) >= 16 KB. ++0.000 write(4, ..., 79000) = 79000 + +// 3a. Inject 6 high-density 35 KB segments (210 KB payload, 222.7 KB truesize +// across 8-page order-3 frags on both CONFIG_MAX_SKB_FRAGS=17 and 45) and +// read 100 bytes from the head SKB so before(skb->seq, tp->copied_seq) is true. ++0.000 < P. 140001:175001(35000) ack 1 win 512 ++0.000 < P. 175001:210001(35000) ack 1 win 512 ++0.000 read(4, ..., 100) = 100 + ++0.000 < P. 210001:245001(35000) ack 1 win 512 ++0.000 < P. 245001:280001(35000) ack 1 win 512 ++0.000 < P. 280001:315001(35000) ack 1 win 512 ++0.000 < P. 315001:350001(35000) ack 1 win 512 + +// 3b. Inject three smaller segments into the remaining advertised rcv_wnd. +// Their higher truesize pushes sk_rmem_alloc > sk_rcvbuf (225000) and +// exhausts sk_forward_alloc, triggering tcp_prune_queue() -> tcp_collapse() +// on the 3rd segment and driving sk->sk_forward_alloc <= -16.4 KB. ++0.000 < P. 350001:350801(800) ack 1 win 512 ++0.000 < P. 350801:351601(800) ack 1 win 512 ++0.000 < P. 351601:351901(300) ack 1 win 512 + +// 4. Drain per-CPU memcg stock via memory.high=0, cap memory.max=0 (O_NONBLOCK +// avoids synchronous reclaim/OOM), and expect -EAGAIN on a 16 KB non-blocking +// write. Because copy (16 KB) minus sk_forward_alloc (<= -16.4 KB) exceeds +// PAGE_ALLOC_COSTLY_ORDER (32 KB), try_charge_memcg() fails without invoking +// the memcg OOM killer. ++0.010 `cgroot=$(mount -t cgroup2 | head -1 | awk '{print $3}') +echo 0 > "${cgroot}/pkt_${PPID}/memory.high" +printf 0 | dd of="${cgroot}/pkt_${PPID}/memory.max" oflag=nonblock status=none` ++0.000 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0 ++0.000 write(4, ..., 16384) = -1 EAGAIN (Resource temporarily unavailable) + ++0.000 close(4) = 0 ++0.000 close(3) = 0 + +// Untimed cleanup command executed by packetdrill on both pass and early failure. +`cgroot=$(mount -t cgroup2 | head -1 | awk '{print $3}') +[ -n "$cgroot" ] || exit 0 +runner_pid=$(awk '/^PPid:/ {print $2}' /proc/$PPID/status) +orig_cg=$(sed -n 's/^0:://p' /proc/$runner_pid/cgroup) +echo $PPID > "${cgroot}${orig_cg}/cgroup.procs" 2>/dev/null || true +echo $$ > "${cgroot}${orig_cg}/cgroup.procs" 2>/dev/null || true +rmdir "${cgroot}/pkt_${PPID}"` -- 2.56.0.307.g5fe7bd680c-goog