Re: What's the correct new API to request pcap_linux to not open an eventfd

[Denis Ovsienko via tcpdump-workers <tcpdump-workers () lists tcpdump org>]

> --- Begin Message ---
>
>
> From: Denis Ovsienko <denis () ovsienko info>
>
> Date: Tue, 5 Jul 2022 12:07:05 +0100
>
> On Fri, 1 Jul 2022 13:55:30 -0400
> Bill Fenner via tcpdump-workers <tcpdump-workers () lists tcpdump org>
> wrote:
>
> > If we set
> > pcap_nonblock after pcap_create and before pcap_activate, we get -3 -
> > which I don't get at all, unless, -3 means "you didn't activate the
> > pcap yet". My naive reading of the Linux pcap_getnonblock code says
> > it'll return the integer value of a bool, and I don't know how that
> > can be -3.
>
> Hello Bill.
>
> The pcap_setnonblock(3PCAP) man page describes two functions:
>
> int pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf);
> int pcap_getnonblock(pcap_t *p, char *errbuf);
>
> If your comments concern pcap_getnonblock(), what you describe is
> consistent with the documented behaviour:
>
> In pcap/pcap.h:
>
> #define PCAP_ERROR_NOT_ACTIVATED        -3      /* the capture needs to
> be activated */
>
> In the man page:
>
> RETURN VALUE
>        pcap_getnonblock()  returns  the  current ``non-blocking''
>        state of the capture descriptor; it always  returns  0  on
>        ``savefiles''.   If  called  on  a capture handle that has
>        been created but not  activated,  PCAP_ERROR_NOT_ACTIVATED
>        is returned.  If there is another error, PCAP_ERROR is re‐
>        turned and errbuf is filled in with an  appropriate  error
>        message.
>
> Did you mean there is an issue with pcap_setnonblock()?
>
> -- 
>     Denis Ovsienko
>
> --- End Message ---
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