````
             rtpxh = (struct rtp_x_hdr *)payload;
      4. tainted_return_value: Function ntohs returns tainted data.
      5. lower_bounds: Casting narrower unsigned ntohs(rtpxh->length) to wider signed type int effectively tests its lower bound.
      6. var_assign_var: Assigning: x_len = ntohs(rtpxh->length) * 4 + 4UL. Both are now tainted.
133                x_len = ntohs(rtpxh->length) * 4 + sizeof(struct rtp_x_hdr);
      7. var_assign_var: Compound assignment involving tainted variable x_len to variable payload taints payload.
134                payload += x_len;
      8. var_assign_var: Compound assignment involving tainted variable x_len to variable payload_len taints payload_len.
135                payload_len -= x_len;
      9. Condition payload_len < 0, taking false branch.
      10. lower_bounds: Checking lower bounds of signed scalar payload_len by taking the false branch of payload_len < 0.
136                if (payload_len < 0) {
137                        DEBUGPC(DLMUX, "received RTP frame too short, "
138                                "extension header exceeds frame length\n");
139                        return NULL;
140                }
141        }
      11. Condition rtph->padding, taking true branch.
142        if (rtph->padding) {
      12. Condition payload_len < 0, taking false branch.
      13. lower_bounds: Checking lower bounds of signed scalar payload_len by taking the false branch of payload_len < 0.
143                if (payload_len < 0) {
144                        DEBUGPC(DLMUX, "received RTP frame too short for "
145                                "padding length\n");
146                        return NULL;
147                }
     
CID 216829: (#1 of 1): Untrusted pointer read (TAINTED_SCALAR)
14. tainted_data: Using tainted variable payload_len - 1 as an index to pointer payload.
      Ensure that tainted values are properly sanitized, by checking that their values are within a permissible range.
````