kernel/linux.git/net/core/dev.c, branch v6.18.22

net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback

2026-04-11T12:26:51+00:00

[ Upstream commit c4336a07eb6b2526dc2b62928b5104b41a7f81f5 ] NETIF_F_IPV6_CSUM only advertises support for checksum offload of packets without IPv6 extension headers. Packets with extension headers must fall back onto software checksumming. Since TSO depends on checksum offload, those must revert to GSO. The below commit introduces that fallback. It always checks network header length. For tunneled packets, the inner header length must be checked instead. Extend the check accordingly. A special case is tunneled packets without inner IP protocol. Such as RFC 6951 SCTP in UDP. Those are not standard IPv6 followed by transport header either, so also must revert to the software GSO path. Cc: stable@vger.kernel.org Fixes: 864e3396976e ("net: gso: Forbid IPv6 TSO with extensions on devices with only IPV6_CSUM") Reported-by: Tangxin Xie Closes: https://lore.kernel.org/netdev/0414e7e2-9a1c-4d7c-a99d-b9039cf68f40@yeah.net/ Suggested-by: Paolo Abeni Signed-off-by: Willem de Bruijn Link: https://patch.msgid.link/20260320190148.2409107-1-willemdebruijn.kernel@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

net: use skb_header_pointer() for TCPv4 GSO frag_off check

2026-04-11T12:26:22+00:00

[ Upstream commit ddc748a391dd8642ba6b2e4fe22e7f2ddf84b7f0 ] Syzbot reported a KMSAN uninit-value warning in gso_features_check() called from netif_skb_features() [1]. gso_features_check() reads iph->frag_off to decide whether to clear mangleid_features. Accessing the IPv4 header via ip_hdr()/inner_ip_hdr() can rely on skb header offsets that are not always safe for direct dereference on packets injected from PF_PACKET paths. Use skb_header_pointer() for the TCPv4 frag_off check so the header read is robust whether data is already linear or needs copying. [1] https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407 Link: https://lore.kernel.org/netdev/willemdebruijn.kernel.1a9f35039caab@gmail.com/ Fixes: cbc53e08a793 ("GSO: Add GSO type for fixed IPv4 ID") Reported-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407 Tested-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com Signed-off-by: Guoyu Su Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260327153507.39742-1-yss2813483011xxl@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: introduce mangleid_features

2026-04-11T12:26:22+00:00

[ Upstream commit 31c5a71d982b57df75858974634c2f0a338f2fc6 ] Some/most devices implementing gso_partial need to disable the GSO partial features when the IP ID can't be mangled; to that extend each of them implements something alike the following[1]: if (skb->encapsulation && !(features & NETIF_F_TSO_MANGLEID)) features &= ~NETIF_F_TSO; in the ndo_features_check() op, which leads to a bit of duplicate code. Later patch in the series will implement GSO partial support for virtual devices, and the current status quo will require more duplicate code and a new indirect call in the TX path for them. Introduce the mangleid_features mask, allowing the core to disable NIC features based on/requiring MANGLEID, without any further intervention from the driver. The same functionality could be alternatively implemented adding a single boolean flag to the struct net_device, but would require an additional checks in ndo_features_check(). Also note that [1] is incorrect if the NIC additionally implements NETIF_F_GSO_UDP_L4, mangleid_features transparently handle even such a case. Signed-off-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/5a7cdaeea40b0a29b88e525b6c942d73ed3b8ce7.1769011015.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski Stable-dep-of: ddc748a391dd ("net: use skb_header_pointer() for TCPv4 GSO frag_off check") Signed-off-by: Sasha Levin

net: Provide a PREEMPT_RT specific check for netdev_queue::_xmit_lock

2026-03-12T11:09:59+00:00

[ Upstream commit b824c3e16c1904bf80df489e293d1e3cbf98896d ] After acquiring netdev_queue::_xmit_lock the number of the CPU owning the lock is recorded in netdev_queue::xmit_lock_owner. This works as long as the BH context is not preemptible. On PREEMPT_RT the softirq context is preemptible and without the softirq-lock it is possible to have multiple user in __dev_queue_xmit() submitting a skb on the same CPU. This is fine in general but this means also that the current CPU is recorded as netdev_queue::xmit_lock_owner. This in turn leads to the recursion alert and the skb is dropped. Instead checking the for CPU number, that owns the lock, PREEMPT_RT can check if the lockowner matches the current task. Add netif_tx_owned() which returns true if the current context owns the lock by comparing the provided CPU number with the recorded number. This resembles the current check by negating the condition (the current check returns true if the lock is not owned). On PREEMPT_RT use rt_mutex_owner() to return the lock owner and compare the current task against it. Use the new helper in __dev_queue_xmit() and netif_local_xmit_active() which provides a similar check. Update comments regarding pairing READ_ONCE(). Reported-by: Bert Karwatzki Closes: https://lore.kernel.org/all/20260216134333.412332-1-spasswolf@web.de Fixes: 3253cb49cbad4 ("softirq: Allow to drop the softirq-BKL lock on PREEMPT_RT") Signed-off-by: Sebastian Andrzej Siewior Reported-by: Bert Karwatzki Signed-off-by: Sebastian Andrzej Siewior Link: https://patch.msgid.link/20260302162631.uGUyIqDT@linutronix.de Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

net: devmem: use READ_ONCE/WRITE_ONCE on binding->dev

2026-03-12T11:09:58+00:00

[ Upstream commit 40bf00ec2ee271df5ba67593991760adf8b5d0ed ] binding->dev is protected on the write-side in mp_dmabuf_devmem_uninstall() against concurrent writes, but due to the concurrent bare reads in net_devmem_get_binding() and validate_xmit_unreadable_skb() it should be wrapped in a READ_ONCE/WRITE_ONCE pair to make sure no compiler optimizations play with the underlying register in unforeseen ways. Doesn't present a critical bug because the known compiler optimizations don't result in bad behavior. There is no tearing on u64, and load omissions/invented loads would only break if additional binding->dev references were inlined together (they aren't right now). This just more strictly follows the linux memory model (i.e., "Lock-Protected Writes With Lockless Reads" in tools/memory-model/Documentation/access-marking.txt). Fixes: bd61848900bf ("net: devmem: Implement TX path") Signed-off-by: Bobby Eshleman Link: https://patch.msgid.link/20260302-devmem-membar-fix-v2-1-5b33c9cbc28b@meta.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: consume xmit errors of GSO frames

2026-03-04T12:20:52+00:00

[ Upstream commit 7aa767d0d3d04e50ae94e770db7db8197f666970 ] udpgro_frglist.sh and udpgro_bench.sh are the flakiest tests currently in NIPA. They fail in the same exact way, TCP GRO test stalls occasionally and the test gets killed after 10min. These tests use veth to simulate GRO. They attach a trivial ("return XDP_PASS;") XDP program to the veth to force TSO off and NAPI on. Digging into the failure mode we can see that the connection is completely stuck after a burst of drops. The sender's snd_nxt is at sequence number N [1], but the receiver claims to have received (rcv_nxt) up to N + 3 * MSS [2]. Last piece of the puzzle is that senders rtx queue is not empty (let's say the block in the rtx queue is at sequence number N - 4 * MSS [3]). In this state, sender sends a retransmission from the rtx queue with a single segment, and sequence numbers N-4*MSS:N-3*MSS [3]. Receiver sees it and responds with an ACK all the way up to N + 3 * MSS [2]. But sender will reject this ack as TCP_ACK_UNSENT_DATA because it has no recollection of ever sending data that far out [1]. And we are stuck. The root cause is the mess of the xmit return codes. veth returns an error when it can't xmit a frame. We end up with a loss event like this: ------------------------------------------------- | GSO super frame 1 | GSO super frame 2 | |-----------------------------------------------| | seg | seg | seg | seg | seg | seg | seg | seg | | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ------------------------------------------------- x ok ok | ok ok ok \\ snd_nxt "x" means packet lost by veth, and "ok" means it went thru. Since veth has TSO disabled in this test it sees individual segments. Segment 1 is on the retransmit queue and will be resent. So why did the sender not advance snd_nxt even tho it clearly did send up to seg 8? tcp_write_xmit() interprets the return code from the core to mean that data has not been sent at all. Since TCP deals with GSO super frames, not individual segment the crux of the problem is that loss of a single segment can be interpreted as loss of all. TCP only sees the last return code for the last segment of the GSO frame (in <> brackets in the diagram above). Of course for the problem to occur we need a setup or a device without a Qdisc. Otherwise Qdisc layer disconnects the protocol layer from the device errors completely. We have multiple ways to fix this. 1) make veth not return an error when it lost a packet. While this is what I think we did in the past, the issue keeps reappearing and it's annoying to debug. The game of whack a mole is not great. 2) fix the damn return codes We only talk about NETDEV_TX_OK and NETDEV_TX_BUSY in the documentation, so maybe we should make the return code from ndo_start_xmit() a boolean. I like that the most, but perhaps some ancient, not-really-networking protocol would suffer. 3) make TCP ignore the errors It is not entirely clear to me what benefit TCP gets from interpreting the result of ip_queue_xmit()? Specifically once the connection is established and we're pushing data - packet loss is just packet loss? 4) this fix Ignore the rc in the Qdisc-less+GSO case, since it's unreliable. We already always return OK in the TCQ_F_CAN_BYPASS case. In the Qdisc-less case let's be a bit more conservative and only mask the GSO errors. This path is taken by non-IP-"networks" like CAN, MCTP etc, so we could regress some ancient thing. This is the simplest, but also maybe the hackiest fix? Similar fix has been proposed by Eric in the past but never committed because original reporter was working with an OOT driver and wasn't providing feedback (see Link). Link: https://lore.kernel.org/CANn89iJcLepEin7EtBETrZ36bjoD9LrR=k4cfwWh046GB+4f9A@mail.gmail.com Fixes: 1f59533f9ca5 ("qdisc: validate frames going through the direct_xmit path") Signed-off-by: Jakub Kicinski Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260223235100.108939-1-kuba@kernel.org Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

net: add a common function to compute features for upper devices

2026-03-04T12:20:50+00:00

[ Upstream commit 28098defc79fe7d29e6bfe4eb6312991f6bdc3d3 ] Some high level software drivers need to compute features from lower devices. But each has their own implementations and may lost some feature compute. Let's use one common function to compute features for kinds of these devices. The new helper uses the current bond implementation as the reference one, as the latter already handles all the relevant aspects: netdev features, TSO limits and dst retention. Suggested-by: Paolo Abeni Signed-off-by: Hangbin Liu Reviewed-by: Sabrina Dubroca Reviewed-by: Jiri Pirko Link: https://patch.msgid.link/20251017034155.61990-2-liuhangbin@gmail.com Signed-off-by: Jakub Kicinski Stable-dep-of: bb4c698633c0 ("team: avoid NETDEV_CHANGEMTU event when unregistering slave") Signed-off-by: Sasha Levin

net: do not pass flow_id to set_rps_cpu()

2026-03-04T12:20:47+00:00

[ Upstream commit 8a8a9fac9efa6423fd74938b940cb7d731780718 ] Blamed commit made the assumption that the RPS table for each receive queue would have the same size, and that it would not change. Compute flow_id in set_rps_cpu(), do not assume we can use the value computed by get_rps_cpu(). Otherwise we risk out-of-bound access and/or crashes. Fixes: 48aa30443e52 ("net: Cache hash and flow_id to avoid recalculation") Signed-off-by: Eric Dumazet Cc: Krishna Kumar Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260220222605.3468081-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: remove WARN_ON_ONCE when accessing forward path array

2026-02-26T22:59:39+00:00

[ Upstream commit 008e7a7c293b30bc43e4368dac6ea3808b75a572 ] Although unlikely, recent support for IPIP tunnels increases chances of reaching this WARN_ON_ONCE if userspace manages to build a sufficiently long forward path. Remove it. Fixes: ddb94eafab8b ("net: resolve forwarding path from virtual netdevice and HW destination address") Signed-off-by: Pablo Neira Ayuso Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin

net: update netdev_lock_{type,name}

2026-01-23T10:21:16+00:00

[ Upstream commit eb74c19fe10872ee1f29a8f90ca5ce943921afe9 ] Add missing entries in netdev_lock_type[] and netdev_lock_name[] : CAN, MCTP, RAWIP, CAIF, IP6GRE, 6LOWPAN, NETLINK, VSOCKMON, IEEE802154_MONITOR. Also add a WARN_ONCE() in netdev_lock_pos() to help future bug hunting next time a protocol is added without updating these arrays. Fixes: 1a33e10e4a95 ("net: partially revert dynamic lockdep key changes") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260108093244.830280-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin