net/ipv4: Send ICMP Destination Unreachable for unknown protocol

[wenquan2015]

Summary

According RFC1122 3.2.2.1, A host SHOULD generate Destination Unreachable messages with code: 2(Protocol Unreachable), when the designated transport protocol is not supported.

Impact

ipv4

Testing

from scapy.all import *

icmp_pkt = IP(dst="10.0.1.2", len=21, proto=143) / "E"

send(icmp_pkt, verbose=1)

test result:

13:38:31.958568 IP 10.0.1.1 > 10.0.1.2: [Ethernet requires IPv6] (invalid)
13:38:31.959701 IP 10.0.1.2 > 10.0.1.1: ICMP 10.0.1.2 protocol 143 unreachable, length 29