Date: Mon, 4 Jan 2010 20:05:23 -0600 From: Peter Steele <psteele@maxiscale.com> To: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: What's the proper way to traverse a getifaddrs() interface list? Message-ID: <7B9397B189EB6E46A5EE7B4C8A4BB7CB36CA401D@MBX03.exg5.exghost.com>
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I have an application where I want to collect information on the network in=
terfaces. I've researched this and the function getifaddrs(struct ifaddrs *=
ifap) appears to be the way to go, but I'm having some trouble understandin=
g exactly how to process the information returned by this call. It's basica=
lly a linked list, but there are two entries for each interface. I initiall=
y thought I could just skip one of the entries but that doesn't appear to b=
e the case, not entirely anyway. What I want to do is write a function that=
returns a list of dynamically allocated structures, one for each interface=
. My structure looks like this:
typedef struct
{
string *ifcId;
string *ipAddr;
bytearray *hwAddr;
string *subnetMask;
string *bcastAddr;
} net_attributes;
and the function I am implementing has the following prototype:
int getAllNetAttributes(net_attributes **result, int **count)
where count is the number of elements in the net_attributes result array. T=
his means I need to first count the number of interfaces and allocate my re=
sult array, and then collect the information for each interface. This means=
two traversals of the linked list, once just to count the entries (the len=
gth of the list divided by 2) and then traversing it again to collect the d=
ata. I've got this mostly working but I'm having trouble with how to deal w=
ith the duplicate entries in the linked list of ifaddrs structures returned=
by getifaddrs. I've looked at ifconfig.c and I can't tell exactly what the=
code is doing as far as how it handles these duplicate entries. Can someon=
e explain the proper way to traverse this linked list?
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