netlink: report why a packet is bad

Replace
 <netlink>: bad IP packet from <source>
with
 <netlink>: bad IP packet from <source>: reason

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/netlink.c b/netlink.c
index df51d9c97e1cfce7f9d5a2fb27880e9099ed5f05..4151e33688dbb91033dc9c90903c3e7202c83cec 100644 (file)
--- a/netlink.c
+++ b/netlink.c
@@ -384,19 +384,29 @@ static void netlink_icmp_simple(struct netlink *st, struct buffer_if *buf,
  * 3. Checksums correctly.
  * 4. Doesn't have a bogus length
  */
  * 3. Checksums correctly.
  * 4. Doesn't have a bogus length
  */

-static bool_t netlink_check(struct netlink *st, struct buffer_if *buf)
+static bool_t netlink_check(struct netlink *st, struct buffer_if *buf,
+                           char *errmsgbuf, int errmsgbuflen)

 {
 {

+#define BAD(...) do{                                   \
+       snprintf(errmsgbuf,errmsgbuflen,__VA_ARGS__);   \
+       return False;                                   \
+    }while(0)
+

     struct iphdr *iph=(struct iphdr *)buf->start;
     int32_t len;
 
     struct iphdr *iph=(struct iphdr *)buf->start;
     int32_t len;
 

-    if (iph->ihl < 5 || iph->version != 4) return False;
-    if (buf->size < iph->ihl*4) return False;
-    if (ip_fast_csum((uint8_t *)iph, iph->ihl)!=0) return False;
+    if (iph->ihl < 5) BAD("ihl %u",iph->ihl);
+    if (iph->version != 4) BAD("version %u",iph->version);
+    if (buf->size < iph->ihl*4) BAD("size %"PRId32"<%u*4",buf->size,iph->ihl);
+    if (ip_fast_csum((uint8_t *)iph, iph->ihl)!=0) BAD("csum");

     len=ntohs(iph->tot_len);
     /* There should be no padding */
     len=ntohs(iph->tot_len);
     /* There should be no padding */

-    if (buf->size!=len || len<(iph->ihl<<2)) return False;
+    if (buf->size!=len) BAD("len %"PRId32"!=%"PRId32,buf->size,len);
+    if (len<(iph->ihl<<2)) BAD("len %"PRId32"<(%u<<2)",len,iph->ihl);

     /* XXX check that there's no source route specified */
     return True;
     /* XXX check that there's no source route specified */
     return True;

+
+#undef BAD

 }
 
 /* Deliver a packet. "client" is the _origin_ of the packet, not its
 }
 
 /* Deliver a packet. "client" is the _origin_ of the packet, not its


@@ -595,11 +605,13 @@ static void netlink_incoming(struct netlink *st, struct netlink_client *client,
 {
     uint32_t source,dest;
     struct iphdr *iph;
 {
     uint32_t source,dest;
     struct iphdr *iph;

+    char errmsgbuf[50];

 
     BUF_ASSERT_USED(buf);
 
     BUF_ASSERT_USED(buf);

-    if (!netlink_check(st,buf)) {
-       Message(M_WARNING,"%s: bad IP packet from %s\n",
-               st->name,client?client->name:"host");
+    if (!netlink_check(st,buf,errmsgbuf,sizeof(errmsgbuf))) {
+       Message(M_WARNING,"%s: bad IP packet from %s: %s\n",
+               st->name,client?client->name:"host",
+               errmsgbuf);

        BUF_FREE(buf);
        return;
     }
        BUF_FREE(buf);
        return;
     }