net: wget-by-hostname + shared DNS resolver (a Game Boy fetches example.com)

resolve.h: shared helper that turns a dotted-quad or a hostname into an IPv4 address (DNS A query over a UDP socket to 1.1.1.1). nslookup now uses it and slims down; wget uses it so you can name a host directly. wget HOST|IP now: resolve -> TCP connect -> "GET / HTTP/1.0" with the real Host header -> stream the body to the LCD/console until EOF. One command does DNS + TCP + HTTP, all on the kernel socket layer. Verified over tunbridge's NAT against the real internet: /# wget example.com connecting 172.66.147.243 HTTP/1.1 200 OK Server: cloudflare <!doctype html><html lang="en"><head><title>Example Domain</title>... </body></html> [eof] The full HTML page arrives across many TCP segments and is reassembled and printed - real DNS, real TCP, real HTTP, fetched by a Game Boy by name. (tunbridge.py already sets up + tears down the NAT, so the demo is a one-liner: sudo python3 tools/tunbridge.py "wget example.com")
author: user <user@clank> 2026-07-17 13:11:53 +0200
committer: user <user@clank> 2026-07-17 13:11:53 +0200
commit: a565bcd942efeb617f5424ae5a881211a7bd0216 (patch)
tree: 518915e70d097ed8f8fee99422bc7161f9c53fc1
parent: net: TCP sockets in the kernel - a Game Boy fetches HTTP over real TCP (diff)
download: gbos-a565bcd942efeb617f5424ae5a881211a7bd0216.tar.gz
gbos-a565bcd942efeb617f5424ae5a881211a7bd0216.tar.xz
gbos-a565bcd942efeb617f5424ae5a881211a7bd0216.zip
3 files changed, 109 insertions, 96 deletions
diff --git a/c/nslookup.c b/c/nslookup.c
index 020a1c1..6a531b8 100644
--- a/c/nslookup.c
+++ b/c/nslookup.c
@@ -1,88 +1,23 @@
-#include "sock.h"
+#include "resolve.h"
 /* nslookup HOST - resolve a hostname to an IPv4 address via DNS over UDP.
-   The kernel owns UDP; this program just builds the DNS query and parses the
-   answer. Queries 1.1.1.1:53 (reachable through the bridge NAT). */
+   All the DNS logic lives in resolve.h (shared with wget). */
 
-/* buf is first and large so 'name' lands past the arg string at 0xA000 */
-static unsigned char buf[200];
-static unsigned char name[64];
-static unsigned char dnssrv[4];
+static unsigned char namebuf[64];     /* first so it lands past the arg at 0xA000 */
 static unsigned char ip[4];
 
-/* build a DNS A-record query for 'host' into buf; return total length */
-static unsigned char build_query(unsigned char *host) {
-    unsigned char i = 0, p = 12, lblpos, len;
-    buf[0] = 0x12; buf[1] = 0x34;          /* id */
-    buf[2] = 0x01; buf[3] = 0x00;          /* flags: recursion desired */
-    buf[4] = 0; buf[5] = 1;                /* qdcount = 1 */
-    buf[6] = 0; buf[7] = 0; buf[8] = 0; buf[9] = 0; buf[10] = 0; buf[11] = 0;
-    while (host[i]) {
-        lblpos = p++; len = 0;
-        while (host[i] && host[i] != '.') { buf[p++] = host[i]; i++; len++; }
-        buf[lblpos] = len;
-        if (host[i] == '.') i++;
-    }
-    buf[p++] = 0;                          /* root label */
-    buf[p++] = 0; buf[p++] = 1;            /* QTYPE  = A  */
-    buf[p++] = 0; buf[p++] = 1;            /* QCLASS = IN */
-    return p;
-}
-
-/* advance past a DNS name at offset p (handles 0xC0 compression pointers) */
-static unsigned int skip_name(unsigned int p) {
-    for (;;) {
-        if (buf[p] == 0) return p + 1;
-        if ((buf[p] & 0xC0) == 0xC0) return p + 2;
-        p += buf[p] + 1;
-    }
-}
-
-/* find the first A record in the response; fill ip[]; return 1 on success */
-static unsigned char parse_answer(void) {
-    unsigned int p, a, an, type, rdlen;
-    an = ((unsigned int)buf[6] << 8) | buf[7];   /* ancount */
-    if (an == 0) return 0;
-    p = skip_name(12) + 4;                        /* skip question (QNAME+QT+QC) */
-    for (a = 0; a < an; a++) {
-        p = skip_name(p);
-        type = ((unsigned int)buf[p] << 8) | buf[p + 1];
-        p += 8;                                   /* TYPE(2)+CLASS(2)+TTL(4) */
-        rdlen = ((unsigned int)buf[p] << 8) | buf[p + 1];
-        p += 2;
-        if (type == 1 && rdlen == 4) {
-            ip[0] = buf[p]; ip[1] = buf[p + 1]; ip[2] = buf[p + 2]; ip[3] = buf[p + 3];
-            return 1;
-        }
-        p += rdlen;
-    }
-    return 0;
-}
-
 void main(void) {
     char *host;
-    unsigned char s, i, qlen, rlen;
+    unsigned char i;
     host = getargs();
     if (!host || !*host) { puts("usage: nslookup HOST"); nl(); sexit(1); }
-    for (i = 0; host[i] && i < 63; i++) name[i] = host[i];   /* arg -> safe buf */
-    name[i] = 0;
-
-    dnssrv[0] = 1; dnssrv[1] = 1; dnssrv[2] = 1; dnssrv[3] = 1;   /* 1.1.1.1 */
-    s = net_socket(SOCK_UDP);
-    if (s == 0xFF) { puts("nslookup: no socket"); nl(); sexit(1); }
-    net_bind(s, 40000);
-    net_connect(s, dnssrv, 53);
-
-    qlen = build_query(name);
-    net_send(s, buf, qlen);
-    rlen = net_recv(s, buf, sizeof(buf));
-    if (rlen == 0xFF) { puts("nslookup: timeout"); nl(); net_close(s); sexit(1); }
+    for (i = 0; host[i] && i < 63; i++) namebuf[i] = (unsigned char)host[i];
+    namebuf[i] = 0;
 
-    if (parse_answer()) {
-        puts((char *)name); puts(" -> ");
+    if (resolve((char *)namebuf, ip)) {
+        puts((char *)namebuf); puts(" -> ");
         for (i = 0; i < 4; i++) { putu(ip[i]); if (i < 3) putc('.'); }
         nl();
     } else {
-        puts("nslookup: no A record"); nl();
+        puts("nslookup: cannot resolve "); puts((char *)namebuf); nl();
     }
-    net_close(s);
 }
diff --git a/c/resolve.h b/c/resolve.h
new file mode 100644
index 0000000..9aaccc1
--- /dev/null
+++ b/c/resolve.h
@@ -0,0 +1,81 @@
+#ifndef RESOLVE_H
+#define RESOLVE_H
+/* resolve.h - turn a dotted-quad OR a hostname into an IPv4 address. Hostname
+   lookups go out as a DNS A query over a UDP socket to 1.1.1.1:53; the kernel
+   owns UDP, this owns DNS. Header-only (one copy per program). */
+#include "sock.h"
+
+static unsigned char _dnsbuf[200];
+static unsigned char _dnssrv[4];
+
+/* parse "A.B.C.D" into out[4]; return 1 on success */
+static unsigned char parse_ip(char *s, unsigned char *out) {
+    unsigned char i, v;
+    for (i = 0; i < 4; i++) {
+        if (*s < '0' || *s > '9') return 0;
+        v = 0;
+        while (*s >= '0' && *s <= '9') { v = (unsigned char)(v * 10 + (*s - '0')); s++; }
+        out[i] = v;
+        if (i < 3) { if (*s != '.') return 0; s++; }
+    }
+    return 1;
+}
+
+static unsigned char _dns_query(char *host) {
+    unsigned char i = 0, p = 12, lblpos, len;
+    _dnsbuf[0] = 0x12; _dnsbuf[1] = 0x34; _dnsbuf[2] = 0x01; _dnsbuf[3] = 0x00;
+    _dnsbuf[4] = 0; _dnsbuf[5] = 1;
+    _dnsbuf[6] = 0; _dnsbuf[7] = 0; _dnsbuf[8] = 0; _dnsbuf[9] = 0; _dnsbuf[10] = 0; _dnsbuf[11] = 0;
+    while (host[i]) {
+        lblpos = p++; len = 0;
+        while (host[i] && host[i] != '.') { _dnsbuf[p++] = host[i]; i++; len++; }
+        _dnsbuf[lblpos] = len;
+        if (host[i] == '.') i++;
+    }
+    _dnsbuf[p++] = 0; _dnsbuf[p++] = 0; _dnsbuf[p++] = 1; _dnsbuf[p++] = 0; _dnsbuf[p++] = 1;
+    return p;
+}
+static unsigned int _dns_skip(unsigned int p) {
+    for (;;) {
+        if (_dnsbuf[p] == 0) return p + 1;
+        if ((_dnsbuf[p] & 0xC0) == 0xC0) return p + 2;
+        p += _dnsbuf[p] + 1;
+    }
+}
+static unsigned char _dns_answer(unsigned char *ip) {
+    unsigned int p, a, an, type, rdlen;
+    an = ((unsigned int)_dnsbuf[6] << 8) | _dnsbuf[7];
+    if (an == 0) return 0;
+    p = _dns_skip(12) + 4;
+    for (a = 0; a < an; a++) {
+        p = _dns_skip(p);
+        type = ((unsigned int)_dnsbuf[p] << 8) | _dnsbuf[p + 1];
+        p += 8;
+        rdlen = ((unsigned int)_dnsbuf[p] << 8) | _dnsbuf[p + 1];
+        p += 2;
+        if (type == 1 && rdlen == 4) {
+            ip[0] = _dnsbuf[p]; ip[1] = _dnsbuf[p + 1]; ip[2] = _dnsbuf[p + 2]; ip[3] = _dnsbuf[p + 3];
+            return 1;
+        }
+        p += rdlen;
+    }
+    return 0;
+}
+
+/* resolve a dotted-quad or hostname into ip[4]; return 1 on success */
+static unsigned char resolve(char *host, unsigned char *ip) {
+    unsigned char s, n;
+    if (parse_ip(host, ip)) return 1;                 /* already an address */
+    _dnssrv[0] = 1; _dnssrv[1] = 1; _dnssrv[2] = 1; _dnssrv[3] = 1;
+    s = net_socket(SOCK_UDP);
+    if (s == 0xFF) return 0;
+    net_bind(s, 40000);
+    net_connect(s, _dnssrv, 53);
+    n = _dns_query(host);
+    net_send(s, _dnsbuf, n);
+    n = net_recv(s, _dnsbuf, 200);
+    net_close(s);
+    if (n == 0xFF) return 0;
+    return _dns_answer(ip);
+}
+#endif
diff --git a/c/wget.c b/c/wget.c
index 9d99eb0..aafbae0 100644
--- a/c/wget.c
+++ b/c/wget.c
@@ -1,39 +1,36 @@
-#include "sock.h"
-/* wget [A.B.C.D] - fetch http://TARGET/ over the kernel TCP socket layer and
-   print it. No SLIP/IP/TCP here: connect() handshakes in the kernel, send()/
-   recv() drive the stream. Default target 10.0.0.1:80 (the SLIP peer/host). */
+#include "resolve.h"
+/* wget HOST|IP - fetch http://HOST/ over the kernel TCP socket layer and print
+   it. Resolves a hostname via DNS first (resolve.h), then connect()/send()/
+   recv() over TCP - all the SLIP/IP/UDP/TCP lives in the kernel. */
 
-static unsigned char buf[220];        /* first + large so dst[] lands arg-safe */
+static unsigned char buf[220];        /* first + large so namebuf/dst land arg-safe */
+static unsigned char namebuf[64];
 static unsigned char dst[4];
 
-static unsigned char parse_ip(char *s, unsigned char *out) {
-    unsigned char i, v;
-    for (i = 0; i < 4; i++) {
-        if (*s < '0' || *s > '9') return 0;
-        v = 0;
-        while (*s >= '0' && *s <= '9') { v = (unsigned char)(v * 10 + (*s - '0')); s++; }
-        out[i] = v;
-        if (i < 3) { if (*s != '.') return 0; s++; }
-    }
-    return 1;
-}
-
 void main(void) {
     char *arg, *r;
     unsigned char s, n, i;
     arg = getargs();
-    if (!arg || !*arg) { dst[0] = 10; dst[1] = 0; dst[2] = 0; dst[3] = 1; }
-    else if (!parse_ip(arg, dst)) { puts("wget: bad address"); nl(); sexit(1); }
+    if (!arg || !*arg) { puts("usage: wget HOST|IP"); nl(); sexit(1); }
+    for (i = 0; arg[i] && i < 63; i++) namebuf[i] = (unsigned char)arg[i];
+    namebuf[i] = 0;
+
+    if (!resolve((char *)namebuf, dst)) {
+        puts("wget: cannot resolve "); puts((char *)namebuf); nl(); sexit(1);
+    }
+    puts("connecting "); for (i = 0; i < 4; i++) { putu(dst[i]); if (i < 3) putc('.'); } nl();
 
     s = net_socket(SOCK_TCP);
     if (s == 0xFF) { puts("wget: no socket"); nl(); sexit(1); }
     net_bind(s, 40001);
-    puts("connecting"); nl();
     if (net_connect(s, dst, 80) == 0xFF) { puts("wget: connect failed"); nl(); net_close(s); sexit(1); }
 
-    r = "GET / HTTP/1.0\r\nHost: gbos\r\n\r\n";
+    /* GET / HTTP/1.0 with the requested host as the Host header */
+    r = "GET / HTTP/1.0\r\nHost: ";
     n = 0;
-    while (r[n]) { buf[n] = r[n]; n++; }
+    while (r[n]) { buf[n] = (unsigned char)r[n]; n++; }
+    for (i = 0; namebuf[i]; i++) buf[n++] = namebuf[i];
+    buf[n++] = '\r'; buf[n++] = '\n'; buf[n++] = '\r'; buf[n++] = '\n';
     net_send(s, buf, n);
 
     for (;;) {
author	user <user@clank>	2026-07-17 13:11:53 +0200
committer	user <user@clank>	2026-07-17 13:11:53 +0200
commit	a565bcd942efeb617f5424ae5a881211a7bd0216 (patch)
tree	518915e70d097ed8f8fee99422bc7161f9c53fc1
parent	net: TCP sockets in the kernel - a Game Boy fetches HTTP over real TCP (diff)
download	gbos-a565bcd942efeb617f5424ae5a881211a7bd0216.tar.gz gbos-a565bcd942efeb617f5424ae5a881211a7bd0216.tar.xz gbos-a565bcd942efeb617f5424ae5a881211a7bd0216.zip