Hello Edward,
On Fri, Jan 15, 2010 at 2:34 PM, Edward Welbourne <eddy@xxxxxxxxx> wrote:
> In man 3 rtnetlink, the example code includes the lines:
>
> rta = (struct rtattr *)(((char *) &req) +
> NLMSG_ALIGN(n->nlmsg_len));
>
> in which the variable "n" is nowhere declared. It seems likely that
> NLMSG_ALIGN(req.nh.nlmsg_len) was intended, albeit I am so deeply
> ignorant of relevant systems that I am learning about them by reading
> man pages, so I may easilly be wrong ...
My guess is that your interpretation is correct, and indeed there are
a few other pieces that look to need similar fixes. I've applied the
patch below, and CCed Andi, who may be offer further
input/confirmation.
> I am also acutely aware of the bug already noted on the man page, but
> you clearly already know about that one !
Yup.
Cheers,
Michael
--- a/man3/rtnetlink.3
+++ b/man3/rtnetlink.3
@@ -84,6 +84,9 @@ This manual page is incomplete.
Creating a rtnetlink message to set the MTU of a device:
.nf
+ #include <linux/rtnetlink.h>
+
+ ...
struct {
struct nlmsghdr nh;
@@ -99,18 +102,18 @@ Creating a rtnetlink message to set the MTU of a device:
memset(&req, 0, sizeof(req));
req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
req.nh.nlmsg_flags = NLM_F_REQUEST;
- req.nh.nlmsg_type = RTML_NEWLINK;
+ req.nh.nlmsg_type = RTM_NEWLINK;
req.if.ifi_family = AF_UNSPEC;
req.if.ifi_index = INTERFACE_INDEX;
req.if.ifi_change = 0xffffffff; /* ???*/
rta = (struct rtattr *)(((char *) &req) +
- NLMSG_ALIGN(n\->nlmsg_len));
+ NLMSG_ALIGN(req.nh.nlmsg_len));
rta\->rta_type = IFLA_MTU;
rta\->rta_len = sizeof(unsigned int);
- req.n.nlmsg_len = NLMSG_ALIGN(req.n.nlmsg_len) +
+ req.n.nlmsg_len = NLMSG_ALIGN(req.nh.nlmsg_len) +
RTA_LENGTH(sizeof(mtu));
memcpy(RTA_DATA(rta), &mtu, sizeof(mtu));
- send(rtnetlink_sk, &req, req.n.nlmsg_len);
+ send(rtnetlink_sk, &req, req.nh.nlmsg_len);
.fi
.SH "SEE ALSO"
.BR netlink (3),
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