On Wed, 18 Nov 2020 00:50:48 +0000 Vadim Fedorenko wrote: > On 17.11.2020 22:38, Jakub Kicinski wrote: > > On Sun, 15 Nov 2020 14:43:48 +0300 Vadim Fedorenko wrote: > >> In case when tcp socket received FIN after some data and the > >> parser haven't started before reading data caller will receive > >> an empty buffer. > > This is pretty terse, too terse for me to understand.. > The flow is simple. Server sends small amount of data right after the > connection is configured and closes the connection. In this case > receiver sees TLS Handshake data, configures TLS socket right after > Change Cipher Spec record. While the configuration is in process, TCP > socket receives small Application Data record, Encrypted Alert record > and FIN packet. So the TCP socket changes sk_shutdown to RCV_SHUTDOWN > and sk_flag with SK_DONE bit set.
Thanks! That's clear. This is a race, right, you can't trigger it reliably? BTW please feel free to add your cases to the tls selftest in tools/testing/selftests. > >> This behavior differs from plain TCP socket and > >> leads to special treating in user-space. Patch unpauses parser > >> directly if we have unparsed data in tcp receive queue. > > Sure, but why is the parser paused? Does it pause itself on FIN? > No, it doesn't start even once. The trace looks like: > > tcp_recvmsg is called > tcp_recvmsg returns 1 (Change Cipher Spec record data) > tls_setsockopt is called > tls_setsockopt returns > tls_recvmsg is called > tls_recvmsg returns 0 > __strp_recv is called > stack > __strp_recv+1 > tcp_read_sock+169 > strp_read_sock+104 > strp_work+68 > process_one_work+436 > worker_thread+80 > kthread+276 > ret_from_fork+34tls_read_size called > > So it looks like strp_work was scheduled after tls_recvmsg and > nothing triggered parser because all the data was received before > tls_setsockopt ended the configuration process. Um. That makes me think we need to flush_work() on the strparser after we configure rx tls, no? Or __unpause at the right time instead of dealing with the async nature of strp_check_rcv()?
