DRiKE · July 16, 2020 18:28 · Jul 16, 2020
diff --git a/xdpblog1-3-parse_dname.c b/xdpblog1-3-parse_dname.c
@@ -0,0 +1,32 @@
+static __always_inline
+uint8_t *parse_dname(struct cursor *c, uint8_t *pkt)
+{
+        uint8_t *dname = c->pos;
+
+        int  i;
+        for (i = 0; i < 128; i++) { /* Maximum 128 labels */
+                uint8_t o;
+
+                if (c->pos + 1 > c->end)
+                        return 0;
+
+                o = *(uint8_t *)c->pos;
+                if ((o & 0xC0) == 0xC0) {
+                        /* Compression label, Only back references! */
+                        if ((o | 0x3F) >= (dname - pkt))
+                                return 0;
+
+                        /* Compression label is the last label of a dname. */
+                        c->pos += 1;
+                        break;
+
+                } else if (o & 0xC0)
+                        /* Unknown label type */
+                        return 0;
+
+                c->pos += o + 1;
+                if (!o)
+                        break;
+        }
+        return dname;
+}