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[2a03:2880:30ff:1::face:b00c]) by smtp.gmail.com with ESMTPSA id k18-20020a056402049200b0056c1cba8480sm2939840edv.25.2024.03.27.13.08.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Mar 2024 13:08:29 -0700 (PDT) From: Breno Leitao To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: quic_jjohnson@quicinc.com, kvalo@kernel.org, leon@kernel.org, dennis.dalessandro@cornelisnetworks.com, Jiri Pirko , Simon Horman , Daniel Borkmann , Lorenzo Bianconi , Coco Li , netdev@vger.kernel.org (open list:NETWORKING DRIVERS), linux-kernel@vger.kernel.org (open list) Subject: [PATCH net-next] net: create a dummy net_device allocator Date: Wed, 27 Mar 2024 13:08:04 -0700 Message-ID: <20240327200809.512867-1-leitao@debian.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org It is impossible to use init_dummy_netdev together with alloc_netdev() as the 'setup' argument. This is because alloc_netdev() initializes some fields in the net_device structure, and later init_dummy_netdev() memzero them all. This causes some problems as reported here: https://lore.kernel.org/all/20240322082336.49f110cc@kernel.org/ Split the init_dummy_netdev() function in two. Create a new function called init_dummy_netdev_core() that does not memzero the net_device structure. Then have init_dummy_netdev() memzero-ing and calling init_dummy_netdev_core(), keeping the old behaviour. init_dummy_netdev_core() is the new function that could be called as an argument for alloc_netdev(). Also, create a helper to allocate and initialize dummy net devices, leveraging init_dummy_netdev_core() as the setup argument. This function basically simplify the allocation of dummy devices, by allocating and initializing it. Freeing the device continue to be done through free_netdev() Suggested-by: Jakub Kicinski Signed-off-by: Breno Leitao --- include/linux/netdevice.h | 3 +++ net/core/dev.c | 55 ++++++++++++++++++++++++++------------- 2 files changed, 40 insertions(+), 18 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index c6f6ac779b34..f4226a99a146 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -4545,6 +4545,9 @@ static inline void netif_addr_unlock_bh(struct net_device *dev) void ether_setup(struct net_device *dev); +/* Allocate dummy net_device */ +struct net_device *alloc_netdev_dummy(int sizeof_priv, const char *name); + /* Support for loadable net-drivers */ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, unsigned char name_assign_type, diff --git a/net/core/dev.c b/net/core/dev.c index 0766a245816b..df2484bbc041 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10340,25 +10340,12 @@ int register_netdevice(struct net_device *dev) } EXPORT_SYMBOL(register_netdevice); -/** - * init_dummy_netdev - init a dummy network device for NAPI - * @dev: device to init - * - * This takes a network device structure and initialize the minimum - * amount of fields so it can be used to schedule NAPI polls without - * registering a full blown interface. This is to be used by drivers - * that need to tie several hardware interfaces to a single NAPI - * poll scheduler due to HW limitations. +/* Initialize the core of a dummy net device. + * This is useful if you are calling this function after alloc_netdev(), + * since it does not memset the net_device fields. */ -void init_dummy_netdev(struct net_device *dev) +static void init_dummy_netdev_core(struct net_device *dev) { - /* Clear everything. Note we don't initialize spinlocks - * are they aren't supposed to be taken by any of the - * NAPI code and this dummy netdev is supposed to be - * only ever used for NAPI polls - */ - memset(dev, 0, sizeof(struct net_device)); - /* make sure we BUG if trying to hit standard * register/unregister code path */ @@ -10379,8 +10366,28 @@ void init_dummy_netdev(struct net_device *dev) * its refcount. */ } -EXPORT_SYMBOL_GPL(init_dummy_netdev); +/** + * init_dummy_netdev - init a dummy network device for NAPI + * @dev: device to init + * + * This takes a network device structure and initialize the minimum + * amount of fields so it can be used to schedule NAPI polls without + * registering a full blown interface. This is to be used by drivers + * that need to tie several hardware interfaces to a single NAPI + * poll scheduler due to HW limitations. + */ +void init_dummy_netdev(struct net_device *dev) +{ + /* Clear everything. Note we don't initialize spinlocks + * are they aren't supposed to be taken by any of the + * NAPI code and this dummy netdev is supposed to be + * only ever used for NAPI polls + */ + memset(dev, 0, sizeof(struct net_device)); + init_dummy_netdev_core(dev); +} +EXPORT_SYMBOL_GPL(init_dummy_netdev); /** * register_netdev - register a network device @@ -10991,6 +10998,18 @@ void free_netdev(struct net_device *dev) } EXPORT_SYMBOL(free_netdev); +/** + * alloc_netdev_dummy - Allocate and initialize a dummy net device. + * @sizeof_priv: size of private data to allocate space for + * @name: device name format string + */ +struct net_device *alloc_netdev_dummy(int sizeof_priv, const char *name) +{ + return alloc_netdev(sizeof_priv, name, NET_NAME_UNKNOWN, + init_dummy_netdev_core); +} +EXPORT_SYMBOL_GPL(alloc_netdev_dummy); + /** * synchronize_net - Synchronize with packet receive processing *