Re: null terminating of IFLA_INFO_KIND/IFLA_IFNAME

On 2/17/21 9:06 AM, Муравьев Александр wrote:

Hi

A noob question that I haven't found an answer.

Just wanted to clarify a piece of iproute2 code.

ip/iplink.c:

quoted

1058         addattr_l(&req.n, sizeof(req), IFLA_INFO_KIND, type,
1059              strlen(type));

also ip/iplink.c:

quoted

1115         addattr_l(&req.n, sizeof(req),
1116               !check_ifname(name) ? IFLA_IFNAME : IFLA_ALT_IFNAME,
1117               name, strlen(name) + 1);

My question is why we skip terminating null character for IFLA_INFO_KIND
(the first case) and don't skip it for IFLA_IFNAME (the second case)? I
mean "strlen(type)" and "strlen(name) + 1".

I think it is just different coders at different points in time. Kernel
side both use nla_strscpy which handles the string terminator (or
missing terminator).