net/icmp: check src ip for icmp request message

[HedongGao]

Summary

According to section 3.2.2.6 of RFC1122, An ICMP Echo Request destined to an IP broadcast or IP multicast address MAY be silently discarded.

Impact

Check src ip for icmp request message, and drop the request message if src ip is broadcast/multicast.

Testing

Set up a SIM environment, ping the SIM from the host side, and verify that normal ping can reply.
Then, write a Python script to construct a multicast/broadcast ICMP request message with the source IP address, where SIM does not respond.

`
from scapy.all import Ether, IP, ICMP, sendp

SRC_MAC = "fa:b1:d9:6d:a0:d3"
DST_MAC = "42:e1:c4:3f:48:dd"
SRC_IP = "224.0.0.1"
DST_IP = "10.0.1.2"
INTERFACE = "eth0"

def send_custom_icmp():
try:
ether_layer = Ether(src=SRC_MAC, dst=DST_MAC)
ip_layer = IP(src=SRC_IP, dst=DST_IP, ttl=64)
icmp_layer = ICMP(type=8, code=0)
full_packet = ether_layer / ip_layer / icmp_layer

    sendp(full_packet, iface=INTERFACE, verbose=True)
    print("\n✅ ICMP packet sent successfully!")
    print(f"📄 Packet details:")
    print(f"   Source MAC: {SRC_MAC} | Destination MAC: {DST_MAC}")
    print(f"   Source IP: {SRC_IP} (Multicast) | Destination IP: {DST_IP}")

except PermissionError:
    print("❌ Insufficient permissions! Run the script with administrator/root privileges (e.g., sudo python3 xxx.py)")
except Exception as e:
    print(f"❌ Failed to send packet: {str(e)}")
    print("💡 Please check: 1. Correct network interface name 2. Valid MAC/IP format 3. Normal network connection")

if name == "main":
send_custom_icmp()
`