kernel/linux.git/include/linux/udp.h, branch v6.19.11

udp: remove busylock and add per NUMA queues

2025-09-23T23:38:39+00:00

busylock was protecting UDP sockets against packet floods, but unfortunately was not protecting the host itself. Under stress, many cpus could spin while acquiring the busylock, and NIC had to drop packets. Or packets would be dropped in cpu backlog if RPS/RFS were in place. This patch replaces the busylock by intermediate lockless queues. (One queue per NUMA node). This means that fewer number of cpus have to acquire the UDP receive queue lock. Most of the cpus can either: - immediately drop the packet. - or queue it in their NUMA aware lockless queue. Then one of the cpu is chosen to process this lockless queue in a batch. The batch only contains packets that were cooked on the same NUMA node, thus with very limited latency impact. Tested: DDOS targeting a victim UDP socket, on a platform with 6 NUMA nodes (Intel(R) Xeon(R) 6985P-C) Before: nstat -n ; sleep 1 ; nstat | grep Udp Udp6InDatagrams 1004179 0.0 Udp6InErrors 3117 0.0 Udp6RcvbufErrors 3117 0.0 After: nstat -n ; sleep 1 ; nstat | grep Udp Udp6InDatagrams 1116633 0.0 Udp6InErrors 14197275 0.0 Udp6RcvbufErrors 14197275 0.0 We can see this host can now proces 14.2 M more packets per second while under attack, and the victim socket can receive 11 % more packets. I used a small bpftrace program measuring time (in us) spent in __udp_enqueue_schedule_skb(). Before: @udp_enqueue_us[398]: [0] 24901 |@@@ | [1] 63512 |@@@@@@@@@ | [2, 4) 344827 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [4, 8) 244673 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ | [8, 16) 54022 |@@@@@@@@ | [16, 32) 222134 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ | [32, 64) 232042 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ | [64, 128) 4219 | | [128, 256) 188 | | After: @udp_enqueue_us[398]: [0] 5608855 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [1] 1111277 |@@@@@@@@@@ | [2, 4) 501439 |@@@@ | [4, 8) 102921 | | [8, 16) 29895 | | [16, 32) 43500 | | [32, 64) 31552 | | [64, 128) 979 | | [128, 256) 13 | | Note that the remaining bottleneck for this platform is in udp_drops_inc() because we limited struct numa_drop_counters to only two nodes so far. Signed-off-by: Eric Dumazet Acked-by: Paolo Abeni Reviewed-by: Willem de Bruijn Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250922104240.2182559-1-edumazet@google.com Signed-off-by: Jakub Kicinski

udp: make busylock per socket

2025-09-18T08:17:10+00:00

While having all spinlocks packed into an array was a space saver, this also caused NUMA imbalance and hash collisions. UDPv6 socket size becomes 1600 after this patch. Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn Reviewed-by: David Ahern Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250916160951.541279-10-edumazet@google.com Reviewed-by: Jakub Kicinski Signed-off-by: Paolo Abeni

net: use NUMA drop counters for softnet_data.dropped

2025-09-14T18:35:17+00:00

Hosts under DOS attack can suffer from false sharing in enqueue_to_backlog() : atomic_inc(&sd->dropped). This is because sd->dropped can be touched from many cpus, possibly residing on different NUMA nodes. Generalize the sk_drop_counters infrastucture added in commit c51613fa276f ("net: add sk->sk_drop_counters") and use it to replace softnet_data.dropped with NUMA friendly softnet_data.drop_counters. This adds 64 bytes per cpu, maybe more in the future if we increase the number of counters (currently 2) per 'struct numa_drop_counters'. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250909121942.1202585-1-edumazet@google.com Signed-off-by: Jakub Kicinski

udp: add drop_counters to udp socket

2025-08-28T11:14:50+00:00

When a packet flood hits one or more UDP sockets, many cpus have to update sk->sk_drops. This slows down other cpus, because currently sk_drops is in sock_write_rx group. Add a socket_drop_counters structure to udp sockets. Using dedicated cache lines to hold drop counters makes sure that consumers no longer suffer from false sharing if/when producers only change sk->sk_drops. This adds 128 bytes per UDP socket. Tested with the following stress test, sending about 11 Mpps to a dual socket AMD EPYC 7B13 64-Core. super_netperf 20 -t UDP_STREAM -H DUT -l10 -- -n -P,1000 -m 120 Note: due to socket lookup, only one UDP socket is receiving packets on DUT. Then measure receiver (DUT) behavior. We can see both consumer and BH handlers can process more packets per second. Before: nstat -n ; sleep 1 ; nstat | grep Udp Udp6InDatagrams 615091 0.0 Udp6InErrors 3904277 0.0 Udp6RcvbufErrors 3904277 0.0 After: nstat -n ; sleep 1 ; nstat | grep Udp Udp6InDatagrams 816281 0.0 Udp6InErrors 7497093 0.0 Udp6RcvbufErrors 7497093 0.0 Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250826125031.1578842-5-edumazet@google.com Signed-off-by: Paolo Abeni

bpf: udp: Make sure iter->batch always contains a full bucket snapshot

2025-05-02T17:54:37+00:00

Require that iter->batch always contains a full bucket snapshot. This invariant is important to avoid skipping or repeating sockets during iteration when combined with the next few patches. Before, there were two cases where a call to bpf_iter_udp_batch may only capture part of a bucket: 1. When bpf_iter_udp_realloc_batch() returns -ENOMEM [1]. 2. When more sockets are added to the bucket while calling bpf_iter_udp_realloc_batch(), making the updated batch size insufficient [2]. In cases where the batch size only covers part of a bucket, it is possible to forget which sockets were already visited, especially if we have to process a bucket in more than two batches. This forces us to choose between repeating or skipping sockets, so don't allow this: 1. Stop iteration and propagate -ENOMEM up to userspace if reallocation fails instead of continuing with a partial batch. 2. Try bpf_iter_udp_realloc_batch() with GFP_USER just as before, but if we still aren't able to capture the full bucket, call bpf_iter_udp_realloc_batch() again while holding the bucket lock to guarantee the bucket does not change. On the second attempt use GFP_NOWAIT since we hold onto the spin lock. Introduce the udp_portaddr_for_each_entry_from macro and use it instead of udp_portaddr_for_each_entry to make it possible to continue iteration from an arbitrary socket. This is required for this patch in the GFP_NOWAIT case to allow us to fill the rest of a batch starting from the middle of a bucket and the later patch which skips sockets that were already seen. Testing all scenarios directly is a bit difficult, but I did some manual testing to exercise the code paths where GFP_NOWAIT is used and where ERR_PTR(err) is returned. I used the realloc test case included later in this series to trigger a scenario where a realloc happens inside bpf_iter_udp_batch and made a small code tweak to force the first realloc attempt to allocate a too-small batch, thus requiring another attempt with GFP_NOWAIT. Some printks showed both reallocs with the tests passing: Apr 25 23:16:24 crow kernel: go again GFP_USER Apr 25 23:16:24 crow kernel: go again GFP_NOWAIT With this setup, I also forced each of the bpf_iter_udp_realloc_batch calls to return -ENOMEM to ensure that iteration ends and that the read() in userspace fails. [1]: https://lore.kernel.org/bpf/CABi4-ogUtMrH8-NVB6W8Xg_F_KDLq=yy-yu-tKr2udXE2Mu1Lg@mail.gmail.com/ [2]: https://lore.kernel.org/bpf/7ed28273-a716-4638-912d-f86f965e54bb@linux.dev/ Signed-off-by: Jordan Rife Signed-off-by: Martin KaFai Lau

udp_tunnel: create a fastpath GRO lookup.

2025-04-09T01:19:41+00:00

Most UDP tunnels bind a socket to a local port, with ANY address, no peer and no interface index specified. Additionally it's quite common to have a single tunnel device per namespace. Track in each namespace the UDP tunnel socket respecting the above. When only a single one is present, store a reference in the netns. When such reference is not NULL, UDP tunnel GRO lookup just need to match the incoming packet destination port vs the socket local port. The tunnel socket never sets the reuse[port] flag[s]. When bound to no address and interface, no other socket can exist in the same netns matching the specified local port. Matching packets with non-local destination addresses will be aggregated, and eventually segmented as needed - no behavior changes intended. Restrict the optimization to kernel sockets only: it covers all the relevant use-cases, and user-space owned sockets could be disconnected and rebound after setup_udp_tunnel_sock(), breaking the uniqueness assumption Note that the UDP tunnel socket reference is stored into struct netns_ipv4 for both IPv4 and IPv6 tunnels. That is intentional to keep all the fastpath-related netns fields in the same struct and allow cacheline-based optimization. Currently both the IPv4 and IPv6 socket pointer share the same cacheline as the `udp_table` field. Signed-off-by: Paolo Abeni Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/41d16bc8d1257d567f9344c445b4ae0b4a91ede4.1744040675.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski

net/udp: Add 4-tuple hash list basis

2024-11-18T11:56:21+00:00

Add a new hash list, hash4, in udp table. It will be used to implement 4-tuple hash for connected udp sockets. This patch adds the hlist to table, and implements helpers and the initialization. 4-tuple hash is implemented in the following patch. hash4 uses hlist_nulls to avoid moving wrongly onto another hlist due to concurrent rehash, because rehash() can happen with lookup(). Co-developed-by: Cambda Zhu Signed-off-by: Cambda Zhu Co-developed-by: Fred Chen Signed-off-by: Fred Chen Co-developed-by: Yubing Qiu Signed-off-by: Yubing Qiu Signed-off-by: Philo Lu Acked-by: Willem de Bruijn Acked-by: Paolo Abeni Signed-off-by: David S. Miller

Merge tag 'printk-for-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2024-05-15T19:34:46+00:00

Pull printk updates from Petr Mladek: - Use no_printk() instead of "if (0) printk()" constructs to avoid generating printk index for messages disabled at compile time - Remove deprecated strncpy/strcpy from printk.c - Remove redundant CONFIG_BASE_FULL in favor of CONFIG_BASE_SMALL * tag 'printk-for-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printk: cleanup deprecated uses of strncpy/strcpy printk: Remove redundant CONFIG_BASE_FULL printk: Change type of CONFIG_BASE_SMALL to bool printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled ceph: Use no_printk() helper dyndbg: Use *no_printk() helpers dev_printk: Add and use dev_no_printk() printk: Let no_printk() use _printk()

printk: Change type of CONFIG_BASE_SMALL to bool

2024-05-06T15:39:09+00:00

CONFIG_BASE_SMALL is currently a type int but is only used as a boolean. So, change its type to bool and adapt all usages: CONFIG_BASE_SMALL == 0 becomes !IS_ENABLED(CONFIG_BASE_SMALL) and CONFIG_BASE_SMALL != 0 becomes IS_ENABLED(CONFIG_BASE_SMALL). Reviewed-by: Petr Mladek Reviewed-by: Greg Kroah-Hartman Reviewed-by: Masahiro Yamada Signed-off-by: Yoann Congal Link: https://lore.kernel.org/r/20240505080343.1471198-3-yoann.congal@smile.fr Signed-off-by: Petr Mladek

net: change maximum number of UDP segments to 128

2024-04-14T16:05:08+00:00

The commit fc8b2a619469 ("net: more strict VIRTIO_NET_HDR_GSO_UDP_L4 validation") adds check of potential number of UDP segments vs UDP_MAX_SEGMENTS in linux/virtio_net.h. After this change certification test of USO guest-to-guest transmit on Windows driver for virtio-net device fails, for example with packet size of ~64K and mss of 536 bytes. In general the USO should not be more restrictive than TSO. Indeed, in case of unreasonably small mss a lot of segments can cause queue overflow and packet loss on the destination. Limit of 128 segments is good for any practical purpose, with minimal meaningful mss of 536 the maximal UDP packet will be divided to ~120 segments. The number of segments for UDP packets is validated vs UDP_MAX_SEGMENTS also in udp.c (v4,v6), this does not affect quest-to-guest path but does affect packets sent to host, for example. It is important to mention that UDP_MAX_SEGMENTS is kernel-only define and not available to user mode socket applications. In order to request MSS smaller than MTU the applications just uses setsockopt with SOL_UDP and UDP_SEGMENT and there is no limitations on socket API level. Fixes: fc8b2a619469 ("net: more strict VIRTIO_NET_HDR_GSO_UDP_L4 validation") Signed-off-by: Yuri Benditovich Reviewed-by: Willem de Bruijn Signed-off-by: David S. Miller