Date: Wed, 18 Jul 2001 07:53:45 -0000 From: "Anand Franklin J" <anandfranklin@hotmail.com> To: freebsd-net@freebsd.org, freebsd-hackers@freebsd.org Subject: Hi(some clarifcation about sysctl usage in ifconfig) Message-ID: <F197ZDgC81TbdkSmLAz000000d2@hotmail.com>
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Hi,
The below code is part of ifconfig which use sysctl:
1:mib[0] = CTL_NET;
2:mib[1] = PF_ROUTE;
3:mib[2] = 0;
4:mib[3] = 0; /* address family */
5:mib[4] = NET_RT_IFLIST;
6:mib[5] = 0;
/* if particular family specified, only ask about it */
7:if (afp)
8: mib[3] = afp->af_af;
9:if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
10: errx(1, "iflist-sysctl-estimate");
11:if ((buf = malloc(needed)) == NULL)
errx(1, "malloc");
12:if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0)
errx(1, "actual retrieval of interface table");
the doubts are:
1) what is the purpose of the above c statements.
2)how are the mib values stored before finding its value
line from 1->8
3)line from 9->11 is clear, that is it finds the length of the buffer to be
allocated.
4)what is the significance of line 12 and what will the buf variable will
contain.
with regard's
franklin.
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