net/arp: dont learn arp information if interface is noarp

[HedongGao]

Summary

When the interface turns off the arp learning capability, it should not learn arp from the IP message even if the ARP_IPIN function is enabled.

Impact

The ARP_IPIN function is invalid for the interface that turns off the arp learning ability.

Testing

1. Enable the CONFIG_ARP_IPIN compilation option and set up the SIM test environment;
2. Set the interface NOARP attribute in SIM;
3. Construct an icmp request message on the host side and send it to the SIM. It is observed that there is no response from the SIM side;
4. The SIM end enables the interface ARP learning capability and sends the icmp request message from the host again. The host end can receive the icmp reply message.

`
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 = "10.0.1.1"
DST_IP = "10.0.1.2"
IFACE = "eth0"

packet = (
Ether(src=SRC_MAC, dst=DST_MAC) /
IP(src=SRC_IP, dst=DST_IP) /
ICMP(type=8, code=0)
)

print("Constructed ICMP Request Packet:")
packet.show()

sendp(packet, iface=IFACE, verbose=1)
print(f"\nICMP request sent from {SRC_IP}({SRC_MAC}) to {DST_IP}({DST_MAC})")
`