On Thu, Sep 28, 2017 at 09:33:46PM +0800, Hangbin Liu wrote:
> From: Hangbin Liu <liuhang...@gmail.com>
>
> This is an update for 460c03f3f3cc ("iplink: double the buffer size also in
> iplink_get()"). After update, we will not need to double the buffer size
> every time when VFs number increased.
>
> With call like rtnl_talk(&rth, &req.n, NULL, 0), we can simply remove the
> length parameter.
>
> With call like rtnl_talk(&rth, nlh, nlh, sizeof(req), I add a new variable
> answer to avoid overwrite data in nlh, because it may has more info after
> nlh. also this will avoid nlh buffer not enough issue.
>
> We need to free answer after using.
>
> Signed-off-by: Hangbin Liu <liuhang...@gmail.com>
> Signed-off-by: Phil Sutter <p...@nwl.cc>
> ---
Reviewed-by: Michal Kubecek <mkube...@suse.cz>
> diff --git a/ip/link_gre.c b/ip/link_gre.c
> index 9ea2970..35782ca 100644
> --- a/ip/link_gre.c
> +++ b/ip/link_gre.c
> @@ -68,7 +68,6 @@ static int gre_parse_opt(struct link_util *lu, int argc,
> char **argv,
> struct {
> struct nlmsghdr n;
> struct ifinfomsg i;
> - char buf[16384];
> } req = {
> .n.nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)),
> .n.nlmsg_flags = NLM_F_REQUEST,
> @@ -76,6 +75,7 @@ static int gre_parse_opt(struct link_util *lu, int argc,
> char **argv,
> .i.ifi_family = preferred_family,
> .i.ifi_index = ifi->ifi_index,
> };
> + struct nlmsghdr *answer = NULL;
> struct rtattr *tb[IFLA_MAX + 1];
> struct rtattr *linkinfo[IFLA_INFO_MAX+1];
> struct rtattr *greinfo[IFLA_GRE_MAX + 1];
> @@ -100,19 +100,20 @@ static int gre_parse_opt(struct link_util *lu, int
> argc, char **argv,
> __u32 erspan_idx = 0;
>
> if (!(n->nlmsg_flags & NLM_F_CREATE)) {
> - if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
> + if (rtnl_talk(&rth, &req.n, &answer) < 0) {
> get_failed:
> fprintf(stderr,
> "Failed to get existing tunnel info.\n");
> + free(answer);
> return -1;
> }
Took me a moment to realize answer is still NULL if we get here via
failed rtnl_talk() but non-NULL if we get here via "goto get_failed"
later. Nice trick. :-)
Michal Kubecek
