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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-06-21 15:43:21 +02:00
Breno Leitao
6c537b845c
find_skb() falls back to np->skb_pool when the GFP_ATOMIC alloc_skb()
fails. The pool is refilled by refill_skbs(), which always allocates
buffers of MAX_SKB_SIZE (ethhdr + iphdr + udphdr + MAX_UDP_CHUNK ==
1502 bytes).
netconsole, however, computes the requested length dynamically as
total_len + np->dev->needed_tailroom
If the egress device declares a non-zero needed_tailroom (e.g. some
tunnel or hardware accelerator devices), the required length can exceed
MAX_SKB_SIZE. The pooled skb is then handed back to the caller, which
immediately performs skb_put(skb, len), trips the tail > end check, and
triggers skb_over_panic().
Leave the normal alloc_skb(len, GFP_ATOMIC) path untouched -- the slab
allocator can still satisfy oversized requests when memory is available,
so senders to devices with non-zero needed_tailroom keep working in the
common case. Only the pool fallback is gated: when alloc_skb() failed
and len exceeds the pool buffer size, skip the skb_dequeue() instead of
burning a pre-allocated skb on a request that would later trip
skb_over_panic(). Reserving pool entries for requests they can actually
satisfy also keeps the panic path, which depends on the pool being
primed, intact.
When that drop happens, emit a rate-limited net_warn() so the user
notices that netconsole is unable to push messages on the egress device.
The warn is skipped under in_nmi() for the same reason schedule_work()
is: printk machinery taken by net_warn_ratelimited() is not NMI-safe and
would risk recursing into the same nbcon console we are servicing.
MAX_SKB_SIZE / MAX_UDP_CHUNK were private to net/core/netpoll.c. Move
them to include/linux/netpoll.h so netconsole can reference the same
definition that refill_skbs() uses, keeping the two in sync by
construction. The header now pulls in <linux/ip.h> and <linux/udp.h>
explicitly so MAX_SKB_SIZE remains self-contained for any future user.
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260604-netcons_fix_before_move-v3-2-ab055b3a6aa5@debian.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
138 lines
3.2 KiB
C
138 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Common code for low-level network console, dump, and debugger code
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*
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* Derived from netconsole, kgdb-over-ethernet, and netdump patches
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*/
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#ifndef _LINUX_NETPOLL_H
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#define _LINUX_NETPOLL_H
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#include <linux/netdevice.h>
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#include <linux/interrupt.h>
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#include <linux/rcupdate.h>
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#include <linux/list.h>
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#include <linux/refcount.h>
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#include <linux/ip.h>
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#include <linux/udp.h>
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union inet_addr {
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__be32 ip;
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struct in6_addr in6;
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};
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/*
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* Maximum payload netpoll's preallocated skb pool can carry. Keep this in
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* sync with the buffer size used by refill_skbs() in net/core/netpoll.c;
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* callers (e.g. netconsole) use it to detect requests the pool can never
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* satisfy and avoid dequeuing a pooled skb that would later trip
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* skb_over_panic() in skb_put().
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*/
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#define MAX_UDP_CHUNK 1460
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#define MAX_SKB_SIZE \
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(sizeof(struct ethhdr) + \
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sizeof(struct iphdr) + \
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sizeof(struct udphdr) + \
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MAX_UDP_CHUNK)
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struct netpoll {
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struct net_device *dev;
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netdevice_tracker dev_tracker;
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/*
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* Either dev_name or dev_mac can be used to specify the local
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* interface - dev_name is used if it is a nonempty string, else
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* dev_mac is used.
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*/
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char dev_name[IFNAMSIZ];
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u8 dev_mac[ETH_ALEN];
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const char *name;
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union inet_addr local_ip, remote_ip;
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bool ipv6;
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u16 local_port, remote_port;
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u8 remote_mac[ETH_ALEN];
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struct sk_buff_head skb_pool;
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struct work_struct refill_wq;
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};
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#define np_info(np, fmt, ...) \
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pr_info("%s: " fmt, np->name, ##__VA_ARGS__)
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#define np_err(np, fmt, ...) \
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pr_err("%s: " fmt, np->name, ##__VA_ARGS__)
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#define np_notice(np, fmt, ...) \
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pr_notice("%s: " fmt, np->name, ##__VA_ARGS__)
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struct netpoll_info {
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refcount_t refcnt;
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struct semaphore dev_lock;
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struct sk_buff_head txq;
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struct delayed_work tx_work;
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struct rcu_head rcu;
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};
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#ifdef CONFIG_NETPOLL
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void netpoll_poll_dev(struct net_device *dev);
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void netpoll_poll_disable(struct net_device *dev);
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void netpoll_poll_enable(struct net_device *dev);
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#else
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static inline void netpoll_poll_disable(struct net_device *dev) { return; }
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static inline void netpoll_poll_enable(struct net_device *dev) { return; }
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#endif
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int __netpoll_setup(struct netpoll *np, struct net_device *ndev);
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int netpoll_setup(struct netpoll *np);
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void __netpoll_free(struct netpoll *np);
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void netpoll_cleanup(struct netpoll *np);
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void do_netpoll_cleanup(struct netpoll *np);
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netdev_tx_t netpoll_send_skb(struct netpoll *np, struct sk_buff *skb);
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void netpoll_zap_completion_queue(void);
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#ifdef CONFIG_NETPOLL
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static inline void *netpoll_poll_lock(struct napi_struct *napi)
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{
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struct net_device *dev = napi->dev;
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if (dev && rcu_access_pointer(dev->npinfo)) {
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int owner = smp_processor_id();
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while (cmpxchg(&napi->poll_owner, -1, owner) != -1)
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cpu_relax();
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return napi;
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}
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return NULL;
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}
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static inline void netpoll_poll_unlock(void *have)
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{
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struct napi_struct *napi = have;
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if (napi)
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smp_store_release(&napi->poll_owner, -1);
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}
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static inline bool netpoll_tx_running(struct net_device *dev)
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{
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return irqs_disabled();
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}
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#else
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static inline void *netpoll_poll_lock(struct napi_struct *napi)
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{
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return NULL;
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}
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static inline void netpoll_poll_unlock(void *have)
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{
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}
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static inline bool netpoll_tx_running(struct net_device *dev)
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{
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return false;
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}
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#endif
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#endif
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