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feat(net): real UDP transport, BSD datagram sockets, DNS resolver, DHCP client

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Turn the networking stubs into a working transport/application stack on top of
the existing L2/L3 (Ethernet/ARP/IPv4/ICMP) core.

UDP (net/ipv4/udp.c)
  - Port-demux table with bound receive handlers, pseudo-header checksum,
    ephemeral-port allocation, limited-broadcast send (0.0.0.0 -> 255.255.255.255
    for DHCP before the interface has an address), and rx/tx/drop counters.
  - Wired into the IPv4 receive path (IP_PROTO_UDP dispatch in net/core/net.c).

BSD sockets (net/core/socket.c)
  - Real SOCK_DGRAM sockets backed by UDP: bind installs a UDP handler that fills
    a per-socket receive ring; send/sendto and recv/recvfrom move datagrams;
    ephemeral auto-bind, connect() memorises the peer. Socket table + I/O stats
    exposed for introspection.

DNS resolver (net/ipv4/dns.c)
  - Builds and parses real A-record queries over UDP/53 (label encoding,
    compression-pointer aware answer walk), cache-first with TTL, static-hosts
    and dotted-quad fast paths, and a bounded timeout that degrades to fallback
    instead of hanging.

DHCP client (net/ipv4/dhcp.c)
  - Full DISCOVER/OFFER/REQUEST/ACK handshake over UDP broadcast, option parsing
    (mask/router/dns/lease/server-id), applies the lease to the primary
    interface, bounded timeouts keep the static config on no response.

Fix (net/ipv4/dns_cache.c): the cache stored IPs as 0xAABBCCDD numeric while the
rest of the stack uses network-byte-order-in-memory (ip_parse/ip_to_str), so a
resolved address came back byte-swapped (nslookup github.com -> 100.121.82.140).
Seeds and dump now use ip_parse/ip_to_str; verified 140.82.121.4.

Userland (lazybox): live ifconfig (real interface + NIC counters, loopback),
netstat with live UDP bindings and transport stats, new `sockstat`, richer
nslookup. Verified in QEMU: boot clean on x86_64/aarch64/armv8i, login as SUB,
ping/nslookup/dhclient/netstat/sockstat all run; DHCP/DNS wire replies are
blocked by the sandbox's slirp but time out cleanly and fall back as designed.

Co-Authored-By: Claude Opus 4.8 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Fh5z6V7nGPbHvqVG5p4CXX
This commit is contained in:
subhobhai943andClaude Opus 4.8 committed 2026-08-26 10:20:58 +05:30
1 parent 2c2e2d536e
commit cd840d5799
10 files changed
+924 -57
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userland/lazybox/lazybox.c
+87 -9
View File
@@ -5,6 +5,9 @@
#include <net/net.h>
#include <net/dns.h>
#include <net/dhcp.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <net/socket.h>
#include <drivers/e1000.h>
#include <drivers/ata.h>
#include <drivers/tty.h>
@@ -882,16 +885,35 @@ static int applet_rmmod(int argc, char** argv) {
static int applet_ifconfig(int argc, char** argv) {
(void)argc; (void)argv;
net_if_t* nif = net_get_primary_if();
uint8_t mac[6];
e1000_get_mac(mac);
printk("eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500\n");
printk(" inet 10.0.2.15 netmask 255.255.255.0 broadcast 10.0.2.2\n");
char ip[16], mask[16], gw[16], dns[16];
if (nif) {
ip_to_str(nif->ip, ip);
ip_to_str(nif->subnet, mask);
ip_to_str(nif->gateway, gw);
ip_to_str(nif->dns, dns);
} else {
strcpy(ip, "0.0.0.0"); strcpy(mask, "0.0.0.0");
strcpy(gw, "0.0.0.0"); strcpy(dns, "0.0.0.0");
}
printk("%s: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500\n",
nif ? nif->name : "eth0");
printk(" inet %s netmask %s gateway %s\n", ip, mask, gw);
printk(" nameserver %s\n", dns);
printk(" ether %02x:%02x:%02x:%02x:%02x:%02x txqueuelen 1000 (Ethernet)\n",
mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
printk(" RX packets 0 bytes 0\n");
printk(" TX packets 0 bytes 0\n");
printk(" RX packets %llu bytes %llu\n",
e1000_get_rx_packets(), e1000_get_rx_bytes());
printk(" TX packets %llu bytes %llu\n",
e1000_get_tx_packets(), e1000_get_tx_bytes());
printk(" Link Status: %s\n", e1000_is_link_up() ? "UP" : "DOWN");
printk("\nlo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536\n");
printk(" inet 127.0.0.1 netmask 255.0.0.0\n");
return 0;
}
@@ -924,11 +946,20 @@ static int applet_dhclient(int argc, char** argv) {
static int applet_nslookup(int argc, char** argv) {
const char* host = (argc >= 2) ? argv[1] : "google.com";
net_if_t* nif = net_get_primary_if();
char srv[16];
ip_to_str(nif ? nif->dns : ip_parse("10.0.2.3"), srv);
uint32_t ip = dns_resolve(host);
if (ip == 0) {
printk("Server:\t\t%s\nAddress:\t%s#53\n\n** server can't find %s: NXDOMAIN\n",
srv, srv, host);
return 1;
}
char ip_buf[16];
ip_to_str(ip, ip_buf);
printk("Server: 10.0.2.3\nAddress: 10.0.2.3#53\n\nNon-authoritative answer:\nName: %s\nAddress: %s\n",
host, ip_buf);
printk("Server:\t\t%s\nAddress:\t%s#53\n\nNon-authoritative answer:\nName:\t%s\nAddress: %s\n",
srv, srv, host, ip_buf);
return 0;
}
@@ -2165,9 +2196,6 @@ static int applet_netstat(int argc, char** argv) {
if (httpd_is_running()) {
printk("tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN (httpd)\n");
}
printk("udp 0 0 0.0.0.0:53 0.0.0.0:* LISTEN (dns)\n");
printk("udp 0 0 0.0.0.0:68 0.0.0.0:* ESTABLISHED (dhcp)\n");
for (size_t i = 0; i < 8; i++) {
const ssh_session_t* s = sshd_get_session(i);
if (s && s->in_use) {
@@ -2177,6 +2205,55 @@ static int applet_netstat(int argc, char** argv) {
client_ip_str, s->client_port, s->username);
}
}
// Live UDP port bindings (DNS resolver, DHCP client, datagram sockets).
uint16_t ports[32];
int np = udp_get_bindings(ports, 32);
for (int i = 0; i < np; i++) {
const char* svc = "";
if (ports[i] == 53) svc = " (dns)";
else if (ports[i] == 68) svc = " (dhcp)";
else if (ports[i] >= 49152) svc = " (ephemeral)";
printk("udp 0 0 0.0.0.0:%-5u 0.0.0.0:*%s\n", ports[i], svc);
}
uint64_t urx, utx, udrop;
udp_get_stats(&urx, &utx, &udrop);
printk(ANSI_YELLOW "\nTransport statistics:\n" ANSI_RESET);
printk(" udp: %llu datagrams received, %llu sent, %llu dropped\n", urx, utx, udrop);
printk(" tcp: %u active connection(s)\n", (unsigned)tcp_get_connections_count());
return 0;
}
// Datagram socket table + UDP transport statistics.
static int applet_sockstat(int argc, char** argv) {
(void)argc; (void)argv;
printk(ANSI_BRIGHT_CYAN "=== SUB-OS Socket Table ===\n" ANSI_RESET);
printk(ANSI_BOLD "%-4s %-8s %-24s %-24s %s\n" ANSI_RESET,
"FD", "TYPE", "LOCAL", "REMOTE", "STATE");
int shown = 0;
for (int i = 0; i < 32; i++) {
const socket_t* s = socket_get(i);
if (!s) continue;
char la[16], ra[16];
ip_to_str(s->local_ip, la);
ip_to_str(s->remote_ip, ra);
char lbuf[24], rbuf[24];
snprintf(lbuf, sizeof(lbuf), "%s:%u", la, s->local_port);
snprintf(rbuf, sizeof(rbuf), "%s:%u", ra, s->remote_port);
const char* ty = (s->type == SOCK_DGRAM) ? "dgram" :
(s->type == SOCK_STREAM) ? "stream" : "raw";
printk("%-4d %-8s %-24s %-24s %s\n", i, ty, lbuf, rbuf,
s->state == 1 ? "CONNECTED" : "OPEN");
shown++;
}
if (!shown) printk(" (no open sockets)\n");
uint64_t tx, rx, drops;
socket_get_stats(&tx, &rx, &drops);
printk("\nSocket I/O: %llu datagrams sent, %llu received, %llu dropped\n",
tx, rx, drops);
return 0;
}
@@ -2495,6 +2572,7 @@ static const lazybox_applet_t applets[] = {
{"nslookup", applet_nslookup, "nslookup <host>", "Query DNS name servers", "Network"},
{"iptables", applet_iptables, "iptables", "Firewall packet filter rules","Network"},
{"netstat", applet_netstat, "netstat", "Network port connections", "Network"},
{"sockstat", applet_sockstat, "sockstat", "Socket table & UDP stats", "Network"},
// Storage & Devices
{"lsblk", applet_lsblk, "lsblk", "List block storage devices", "Storage"},