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#include "sock.h"
/* dhcp - a minimal DHCP client. DISCOVER -> OFFER -> REQUEST -> ACK over UDP
(kernel owns UDP; this owns BOOTP/DHCP), then hands the leased address to the
kernel with net_setip(). Run at boot before the shell. Times out gracefully
if there's no server (the shell then comes up unconfigured). */
static unsigned char pkt[288]; /* BOOTP is ~240B + options (frames > 255) */
static unsigned char ip[4];
static unsigned char bcast[4];
/* fill the fixed BOOTP request header + magic cookie; options start at 240 */
static void bootp(void) {
unsigned int i;
for (i = 0; i < 240; i++) pkt[i] = 0;
pkt[0] = 1; pkt[1] = 1; pkt[2] = 6; /* op=request htype=eth hlen=6 */
pkt[4] = 0x12; pkt[5] = 0x34; pkt[6] = 0x56; pkt[7] = 0x78; /* xid */
pkt[10] = 0x80; /* flags: broadcast reply */
pkt[28] = 0x02; pkt[29] = 0x47; pkt[30] = 0x42; pkt[33] = 0x01; /* client MAC */
pkt[236] = 0x63; pkt[237] = 0x82; pkt[238] = 0x53; pkt[239] = 0x63; /* magic */
}
/* DHCP message type from the received packet (option 53), or 0 */
static unsigned char mtype(void) {
unsigned int p = 240;
while (p < 280 && pkt[p] != 255) {
if (pkt[p] == 0) { p++; continue; } /* pad */
if (pkt[p] == 53) return pkt[p + 2];
p += 2 + pkt[p + 1];
}
return 0;
}
void main(void) {
unsigned char s, i, n;
unsigned int p;
bcast[0] = 255; bcast[1] = 255; bcast[2] = 255; bcast[3] = 255;
puts("dhcp: discovering"); nl();
s = net_socket(SOCK_UDP);
if (s == 0xFF) { puts("dhcp: no socket"); nl(); return; }
net_bind(s, 68);
net_connect(s, bcast, 67);
/* DISCOVER -> OFFER (retry a few times for startup timing) */
bootp();
p = 240;
pkt[p++] = 53; pkt[p++] = 1; pkt[p++] = 1; /* DHCPDISCOVER */
pkt[p++] = 255;
n = 0xFF;
for (i = 0; i < 3 && n == 0xFF; i++) {
net_send(s, pkt, (unsigned char)p);
n = net_recv(s, pkt, 255);
}
if (n == 0xFF || mtype() != 2) { puts("dhcp: no offer"); nl(); net_close(s); return; }
ip[0] = pkt[16]; ip[1] = pkt[17]; ip[2] = pkt[18]; ip[3] = pkt[19]; /* yiaddr */
/* REQUEST -> ACK */
bootp();
p = 240;
pkt[p++] = 53; pkt[p++] = 1; pkt[p++] = 3; /* DHCPREQUEST */
pkt[p++] = 50; pkt[p++] = 4; /* requested IP */
pkt[p++] = ip[0]; pkt[p++] = ip[1]; pkt[p++] = ip[2]; pkt[p++] = ip[3];
pkt[p++] = 255;
net_send(s, pkt, (unsigned char)p);
n = net_recv(s, pkt, 255);
net_close(s);
if (n == 0xFF || mtype() != 5) { puts("dhcp: request failed"); nl(); return; }
ip[0] = pkt[16]; ip[1] = pkt[17]; ip[2] = pkt[18]; ip[3] = pkt[19];
net_setip(ip);
puts("dhcp: leased "); for (i = 0; i < 4; i++) { putu(ip[i]); if (i < 3) putc('.'); } nl();
}
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