Bjorn Mork wrote:
No, an ICMP echo reply does not include the entire request packets
RFC792:
The data received in the echo message must be returned in the echo
reply message.
RFC792:
Echo or Echo Reply Message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+-
The data excludes IP and ICMP header and is not "the entire
request packets".
Once an echo request packet is reassembled, which may cause
buffer overflow with poor implementations, you only have to
rewrite type, checksum and IP header to construct echo reply
without copying data, which is what BSD kernel is doing.
Masataka Ohta
