On Tue, Apr 30, 2024 at 01:18:29PM +0300, Evgen Bendyak wrote: > This patch addresses a bug that occurs when the nflog_open function is > called concurrently from different threads within an application. The > function nflog_open internally invokes nflog_open_nfnl. Within this > function, a static global variable pkt_cb (static struct nfnl_callback > pkt_cb) is used. This variable is assigned a pointer to a newly > created structure (pkt_cb.data = h;) and is passed to > nfnl_callback_register. The issue arises with concurrent execution of > pkt_cb.data = h;, as only one of the simultaneously created > nflog_handle structures is retained due to the callback function. > Subsequently, the callback function __nflog_rcv_pkt is invoked for all > the nflog_open structures, but only references one of them. > Consequently, the callbacks registered by the end-user of the library > through nflog_callback_register fail to trigger in sessions where the > incorrect reference was recorded. > This patch corrects this behavior by creating the structure locally on > the stack for each call to nflog_open_nfnl. Since the > nfnl_callback_register function simply copies the data into its > internal structures, there is no need to retain pkt_cb beyond this > point. Out of curiosity: How do you use this? There is a fanout feature to distribute packets between consumer threads to scale up. And I suspect you don't want packets that belong to the same flow be handled by different threads.
