Am 03.02.2022 um 15:51 schrieb Matthias Paul:
Hello all,I'm using lwip 2.1.2 in non-OS / non-threaded mode (main loop mode) with raw API to send/receive TCP packets. When sending packets with tcp_write() I'd like to use zero copy mechanism. Therefore I need to keep the pbuf objects until the buffer has been sent and acknowledged by the recipient. When acknowledged, my callback registered by tcp_sent() is called: static err_t TCPSERVER_sentCallback( void * arg, struct tcp_pcb * tcpPcb, uint16_t length) { // remove pbuf which are reported as "sent" ... } Is "length" always matching a single pbuf length or could it happen that TCPSERVER_sentCallback() reports multiple pbuf objects at once? Also, can I assume, that TCPSERVER_sentCallback() is called in the order the packets have been sent?
You have to understand the tcp protocol to understand the sent callback: a host acknowledges the bytes received from a the other side. It is free to send an ACK for an arbitrary byte count between 1 and the maxiumum outstanding bytes. But since tcp is a streaming protocol, you'll always know when to free the next buffer from the from of your list when you sum up the 'length' parameter of all 'sent' calls. Regards, Simon _______________________________________________ lwip-users mailing list lwip-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/lwip-users
