Merge pull request #1368 from pbhole/fix_dns_matching

examples: fix dns_matching

examples/networking/dns_matching/dns_matching.c

@@ -43,7 +43,7 @@ struct dns_char_t
 } BPF_PACKET_HEADER;
 
 struct Key {
-  unsigned char p[32];
+  unsigned char p[255];
 };
 
 struct Leaf {
@@ -70,10 +70,6 @@ int dns_matching(struct __sk_buff *skb)
       struct udp_t *udp = cursor_advance(cursor, sizeof(*udp));
       if(udp->dport == 53){
 
-        // Our Cursor + the length of our udp packet - size of the udp header
-        // - the two 16bit values for QTYPE and QCLASS.
-        u8 *sentinel = cursor + udp->length - sizeof(*udp) - 4;
-
         struct dns_hdr_t *dns_hdr = cursor_advance(cursor, sizeof(*dns_hdr));
 
         // Do nothing if packet is not a request.
@@ -84,17 +80,19 @@ int dns_matching(struct __sk_buff *skb)
 
         u16 i = 0;
         struct dns_char_t *c;
-        // This unroll worked not in latest BCC version.
-        for(u8 j = 0; i<255;i++){
-          if (cursor == sentinel) goto end; c = cursor_advance(cursor, 1); key.p[i++] = c->c;
+        #pragma unroll
+        for(i = 0; i<255;i++){
+          c = cursor_advance(cursor, 1);
+          if (c->c == 0)
+            break;
+          key.p[i] = c->c;
         }
-        end:
-        {}
 
         struct Leaf * lookup_leaf = cache.lookup(&key);
 
         // If DNS name is contained in our map, drop packet.
         if(lookup_leaf) {
+          bpf_trace_printk("Matched1\n");
           return 0;
         }
       }

examples/networking/dns_matching/dns_matching.py

@@ -11,8 +11,8 @@ import struct
 
 
 def encode_dns(name):
-  size = 32
-  if len(name) > 253:
+  size = 255
+  if len(name) > 255:
     raise Exception("DNS Name too long.")
   b = bytearray(size)
   i = 0;