nstack is a Linux userspace TCP/IP stack. It was constructed to meet the following goals:

• Learn TCP/IP
• Learn Linux systems/network programming
• Learn Linux Socket API

Current features:

• One network interface and socket
• thernet II frame handling
• ARP request/reply, simple caching
• ICMP pings and replies
• IPv4 packet handling, checksum
• TCPv4 Handshake
• TCP data transmission

make

Set up test environment:

tools/testenv.sh start
tools/run.sh veth1

Execute ping inside test environment:

tools/ping_test.sh

Expected nstack messages:

arp_gratuitous: Announce 10.0.0.2
nstack_ingress_thread: Waiting for rx
nstack_ingress_thread: Frame received!
ether_input: proto id: 0x800
ip_input: proto id: 0x1
icmp_input: ICMP type: 8
nstack_ingress_thread: tick
nstack_ingress_thread: Waiting for rx
nstack_ingress_thread: Frame received!
ether_input: proto id: 0x800
ip_input: proto id: 0x1
icmp_input: ICMP type: 8

• Level-IP and informative blog
• Linux kernel TCP/IP stack
• picoTCP
• tapip