tcpdump mailing list archives
Re: What's the correct new API to request pcap_linux to not open an eventfd
From: Bill Fenner via tcpdump-workers <tcpdump-workers () lists tcpdump org>
Date: Tue, 5 Jul 2022 09:28:14 -0400
--- Begin Message --- From: Bill Fenner <fenner () gmail com>
Date: Tue, 5 Jul 2022 09:28:14 -0400
Hi Denis, Thanks for pointing out the manpage update. I had old man pages (my work is being done in the context of the 1.10 release). What confused me is the asymmetry of the API. If you call pcap_setnonblock() on an un-activated socket, it sets a flag and doesn't return an error. But pcap_getnonblock() returns an error, so you can not check the value on an un-activated socket. This is not a flaw, necessarily, just confusing. Now that I understand this flow (I did not realize there were two different implementations of pcap_setnonblock(), because I was focused on pcap-linux.c and not on the important stuff in pcap.c) I think it's straightforward to defer the opening of the eventfd to pcap_activate(), so that we can avoid opening the eventfd altogether in nonblock mode. I'll see if I can update my changes accordingly. Thank you for pointing out the extra detail that helped me to understand. Bill
--- End Message ---
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Current thread:
- Re: What's the correct new API to request pcap_linux to not open an eventfd Bill Fenner via tcpdump-workers (Jul 01)
- Re: What's the correct new API to request pcap_linux to not open an eventfd Denis Ovsienko via tcpdump-workers (Jul 05)
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- Re: What's the correct new API to request pcap_linux to not open an eventfd Bill Fenner via tcpdump-workers (Jul 05)