Re: [PATCH 2.6 NET] Adjust RTATTR_MAX to IFLA_* changes

["David S. Miller" <davem@xxxxxxxxxxxxx>]

On Thu, 9 Sep 2004 18:31:31 +0200
Thomas Graf <tgraf@xxxxxxx> wrote:

> IFLA_MAX is now bigger than RTA_MAX with the latest changes in IFLA_*.
> Adjust RTATTR to point to IFLA_MAX to have big enough buffer in
> rtnetlink_rcv_msg.

Ok, this is going to get silly if some other attribute gets
larger than IFLA_* next.

We should just compute this thing at run time.
Else, if the macro can't be deleted because there
are non-trivial other uses, use some expression
involving max().

I just checked iproute2 sources and it does not reference
this thing, so probably best to kill it off, like so.

===== include/linux/rtnetlink.h 1.42 vs edited =====
--- 1.42/include/linux/rtnetlink.h      2004-09-02 13:12:43 -07:00
+++ edited/include/linux/rtnetlink.h    2004-09-09 10:10:08 -07:00
@@ -660,10 +660,6 @@
 #define TCA_PAYLOAD(n) NLMSG_PAYLOAD(n,sizeof(struct tcmsg))
 
 
-/* SUMMARY: maximal rtattr understood by kernel */
-
-#define RTATTR_MAX             RTA_MAX
-
 /* RTnetlink multicast groups */
 
 #define RTMGRP_LINK            1
===== net/core/rtnetlink.c 1.24 vs edited =====
--- 1.24/net/core/rtnetlink.c   2004-09-02 13:12:43 -07:00
+++ edited/net/core/rtnetlink.c 2004-09-09 10:08:44 -07:00
@@ -401,6 +401,10 @@
        return 0;
 }
 
+/* Protected by RTNL sempahore.  */
+static struct rtattr **rta_buf;
+static int rtattr_max;
+
 /* Process one rtnetlink message. */
 
 static __inline__ int
@@ -408,8 +412,6 @@
 {
        struct rtnetlink_link *link;
        struct rtnetlink_link *link_tab;
-       struct rtattr   *rta[RTATTR_MAX];
-
        int sz_idx, kind;
        int min_len;
        int family;
@@ -476,7 +478,7 @@
                return -1;
        }
 
-       memset(&rta, 0, sizeof(rta));
+       memset(rta_buf, 0, (rtattr_max * sizeof(struct rtattr *)));
 
        min_len = rtm_min[sz_idx];
        if (nlh->nlmsg_len < min_len)
@@ -491,7 +493,7 @@
                        if (flavor) {
                                if (flavor > rta_max[sz_idx])
                                        goto err_inval;
-                               rta[flavor-1] = attr;
+                               rta_buf[flavor-1] = attr;
                        }
                        attr = RTA_NEXT(attr, attrlen);
                }
@@ -501,7 +503,7 @@
                link = &(rtnetlink_links[PF_UNSPEC][type]);
        if (link->doit == NULL)
                goto err_inval;
-       err = link->doit(skb, nlh, (void *)&rta);
+       err = link->doit(skb, nlh, (void *)&rta_buf[0]);
 
        *errp = err;
        return err;
@@ -621,6 +623,16 @@
 
 void __init rtnetlink_init(void)
 {
+       int i;
+
+       rtattr_max = 0;
+       for (i = 0; i < ARRAY_SIZE(rta_max); i++)
+               if (rta_max[i] > rtattr_max)
+                       rtattr_max = rta_max[i];
+       rta_buf = kmalloc(rtattr_max * sizeof(struct rtattr *), GFP_KERNEL);
+       if (!rta_buf)
+               panic("rtnetlink_init: cannot allocate rta_buf\n");
+
        rtnl = netlink_kernel_create(NETLINK_ROUTE, rtnetlink_rcv);
        if (rtnl == NULL)
                panic("rtnetlink_init: cannot initialize rtnetlink\n");