bios: add BOOTP support to libliteeth

This adds BOOTP support as per RFC 951 and RFC 1532. Since most recent
BOOTP servers seem to require the magic cookie defined in RFC 1533, this
is also included.

N.b.: the secs field is set to the uptime, even though RFC 1532
specifies this as the time since the first BOOTREQUEST. Since the BIOS
usually won't be running for that long and the field is often ignored by
servers, this felt like a reasonable compromise.

Signed-off-by: Matthias Breithaupt <m.breithaupt@vogl-electronic.com>

litex/soc/software/libliteeth/Makefile

@@ -1,7 +1,7 @@
 include ../include/generated/variables.mak
 include $(SOC_DIRECTORY)/software/common.mak
 
-OBJECTS=udp.o tftp.o mdio.o
+OBJECTS=udp.o bootp.o tftp.o mdio.o
 
 all: libliteeth.a
 

litex/soc/software/libliteeth/bootp.c

@@ -0,0 +1,193 @@
+// This file is Copyright (c) 2024 Matthias Breithaupt <m.breithaupt@vogl-electronic.com>
+
+// License: BSD
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <libbase/lfsr.h>
+
+#include <libliteeth/inet.h>
+#include <libliteeth/udp.h>
+#include <libliteeth/bootp.h>
+
+#define PORT_SERVER     67
+#define PORT_CLIENT     68
+
+#define OP_BOOTREQUEST  1
+#define OP_BOOTREPLY    2
+
+#define HTYPE_ETHERNET  1
+
+#define HLEN_ETHERNET   6
+
+#define FLAG_BROADCAST  0x8000
+
+#define MAGIC_COOKIE    0x63825363
+
+typedef struct {
+    uint8_t op;
+    uint8_t htype;
+    uint8_t hlen;
+    uint8_t hops;
+    uint32_t xid;
+    uint16_t secs;
+    uint16_t flags;
+    uint32_t ciaddr;
+    uint32_t yiaddr;
+    uint32_t siaddr;
+    uint32_t giaddr;
+    uint8_t chaddr[6];
+    uint8_t pad[10];
+    uint8_t sname[64];
+    uint8_t file[128];
+    uint32_t cookie;
+    uint8_t vend[60];
+} __attribute__((packed)) bootp_message;
+
+static unsigned int seed = 0;
+
+static void seed_from_mac(const unsigned char* macaddr)
+{
+	seed = macaddr[2] << 24 | macaddr[3] << 16 | macaddr[4] << 8 | macaddr[5];
+}
+
+static uint32_t rand32(void)
+{
+#ifdef CSR_TIMER0_UPTIME_CYCLES_ADDR
+	timer0_uptime_latch_write(1);
+	seed = timer0_uptime_cycles_read();
+#endif
+	uint32_t ret = lfsr(32, seed);
+	seed = ret;
+	return ret;
+}
+
+static int format_request(uint8_t *buf, uint32_t xid, const unsigned char* macaddr)
+{
+	uint16_t flags = FLAG_BROADCAST;
+	uint16_t uptime = 0;
+#ifdef CSR_TIMER0_UPTIME_CYCLES_ADDR
+	timer0_uptime_latch_write(1);
+	uptime = timer0_uptime_cycles_read()/CONFIG_CLOCK_FREQUENCY
+#endif
+
+	bootp_message *msg = (bootp_message*) buf;
+	msg->op = OP_BOOTREQUEST;
+	msg->htype = HTYPE_ETHERNET;
+	msg->hlen = HLEN_ETHERNET;
+	msg->hops = 0;
+	msg->xid = htonl(xid);
+	msg->secs = htons(uptime);
+	msg->flags = htons(flags);
+	msg->ciaddr = 0;
+	msg->yiaddr = 0;
+	msg->siaddr = 0;
+	msg->giaddr = 0;
+	memcpy(msg->chaddr, macaddr, 6);
+	memset(msg->pad, 0, sizeof(msg->pad));
+	memset(msg->sname, 0, sizeof(msg->sname));
+	memset(msg->file, 0, sizeof(msg->file));
+	msg->cookie = htonl(MAGIC_COOKIE);
+	memset(msg->vend, 0, sizeof(msg->vend));
+	return 300;
+}
+
+static uint32_t xid;
+static uint8_t response_received;
+
+static unsigned char mymac[6];
+static uint32_t client_ip;
+static uint32_t server_ip;
+static char filename[128];
+
+static uint8_t got_ip;
+
+static void rx_callback(uint32_t src_ip, uint16_t src_port,
+    uint16_t dst_port, void *buf, unsigned int length)
+{
+	bootp_message *msg;
+	if(length < 300) return;
+	msg = (bootp_message*) buf;
+	if(dst_port != PORT_CLIENT) return;
+	if(msg->op != OP_BOOTREPLY) return;
+	if(msg->htype != HTYPE_ETHERNET) return;
+	if(msg->hlen != HLEN_ETHERNET) return;
+	if(msg->hops != 0) return;
+	if(ntohl(msg->xid) != xid) return;
+	if(memcmp(msg->chaddr, mymac, 6) != 0) return;
+	client_ip = ntohl(msg->yiaddr);
+	server_ip = ntohl(msg->siaddr);
+	memcpy(filename, msg->file, sizeof(filename));
+	filename[sizeof(filename) - 1] = 0;
+	response_received = 1;
+}
+
+int bootp_get(const unsigned char *macaddr, uint32_t *_client_ip,
+    uint32_t *_server_ip, char *_filename, size_t _len_filename,
+    uint8_t force)
+{
+	int len, tries, i;
+	int ret = -1;
+        uint8_t *packet_data;
+	uint8_t len_filename = 128;
+
+	if (_len_filename < 128) {
+		len_filename = _len_filename;
+	}
+	if (got_ip && !force) {
+		ret = 0;
+		goto copy;
+	}
+	response_received = 0;
+	memcpy(mymac, macaddr, 6);
+
+	client_ip = udp_get_ip();
+	udp_set_ip(IPTOINT(0, 0, 0, 0));
+
+#ifndef CSR_TIMER0_UPTIME_CYCLES_ADDR
+	if(seed == 0) {
+		seed_from_mac(macaddr);
+	}
+#endif
+
+	udp_set_broadcast_callback((udp_callback) rx_callback);
+
+	tries = 3;
+
+	while(1) {
+		xid = rand32();
+		
+		packet_data = udp_get_tx_buffer();
+		len = format_request(packet_data, xid, macaddr);
+
+		udp_set_broadcast();
+		udp_send(PORT_CLIENT, PORT_SERVER, len);
+		for(i=0;i<100000;i++) {
+			udp_service();
+			if(response_received) break;
+		}
+		if(response_received) break;
+		tries--;
+		if(tries == 0) {
+			ret = -1;
+			goto end;
+		}
+	}
+
+	ret = 0;
+	got_ip = 1;
+copy:
+	*_server_ip = server_ip;
+	len = strlen(filename);
+	memcpy(_filename, filename, len_filename);
+	_filename[len_filename - 1] = 0;
+
+end:
+	*_client_ip = client_ip;
+	udp_set_broadcast_callback(NULL);
+	udp_set_ip(client_ip);
+
+	return ret;
+}

litex/soc/software/libliteeth/bootp.h

@@ -0,0 +1,21 @@
+#ifndef __BOOTP_H
+#define __BOOTP_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+
+int bootp_get(const unsigned char *macaddr, uint32_t *client_ip,
+    uint32_t *server_ip, char *filename, size_t len_filename,
+    uint8_t force);
+
+int bootp_has_ip(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __BOOTP_H */
+