dhcpserver: Initial DHCP server support, hands out leases but doesn't expire them

extras/dhcpserver/component.mk

@@ -0,0 +1,11 @@
+# Component makefile for extras/dhcpserver
+
+#error IWASERROR
+
+INC_DIRS += $(ROOT)extras/dhcpserver/include
+
+# args for passing into compile rule generation
+extras/dhcpserver_INC_DIR =  $(ROOT)extras/dhcpserver
+extras/dhcpserver_SRC_DIR =  $(ROOT)extras/dhcpserver
+
+$(eval $(call component_compile_rules,extras/dhcpserver))

extras/dhcpserver/dhcpserver.c

@@ -0,0 +1,279 @@
+/* Very basic LWIP & FreeRTOS-based DHCP server
+
+   Based on RFC2131 http://www.ietf.org/rfc/rfc2131.txt
+   ... although not fully RFC compliant yet.
+ */
+#include <string.h>
+
+#include <FreeRTOS.h>
+#include <task.h>
+
+#include <lwip/netif.h>
+#include <lwip/api.h>
+#include <lwip/dhcp.h>
+#include <lwip/netbuf.h>
+
+#include "dhcpserver.h"
+
+typedef struct {
+    uint8_t hwaddr[NETIF_MAX_HWADDR_LEN];
+    uint32_t expires;
+} dhcp_lease_t;
+
+typedef struct {
+    struct netconn *nc;
+    dhcp_lease_t leases[DHCPSERVER_MAXCLIENTS];
+    struct netif *server_if;
+} server_state_t;
+
+/* Handlers for various kinds of incoming DHCP messages */
+static void handle_dhcp_discover(server_state_t *state, struct dhcp_msg *received);
+static void handle_dhcp_request(server_state_t *state, struct dhcp_msg *dhcpmsg);
+
+/* Utility functions */
+static uint8_t *find_dhcp_option(struct dhcp_msg *msg, uint8_t option_num, uint8_t min_length, uint8_t *length);
+static uint8_t *add_dhcp_option_byte(uint8_t *opt, uint8_t type, uint8_t value);
+static uint8_t *add_dhcp_option_bytes(uint8_t *opt, uint8_t type, void *value, uint8_t len);
+static dhcp_lease_t *find_lease_slot(dhcp_lease_t *leases, uint8_t *hwaddr);
+
+static void dhcpserver_task(void *pxParameter)
+{
+    server_state_t state = {
+        /* TODO: allow server interface to be specified as argument to dhcpserver_start() */
+        .server_if = netif_list,
+    };
+
+    state.nc = netconn_new (NETCONN_UDP);
+    if(!state.nc) {
+        printf("OTA TFTP: Failed to allocate socket.\r\n");
+        return;
+    }
+
+    /* Seems in LWIP we need to bind to IP_ADDR_ANY to receive broadcasts.
+
+       No way I can find to either bind only on a particular interface (server_if),
+       or to filter incoming broadcasts to only accept those on a single interface,
+       when the REQUEST arrives the from address is 0.0.0.0 and to is 255.255.255.255,
+       and the pbuf doesn't know about the interface it came in on... :/
+     */
+    netconn_bind(state.nc, IP_ADDR_ANY, DHCP_SERVER_PORT);
+
+    while(1)
+    {
+        struct netbuf *netbuf;
+        struct dhcp_msg received = { 0 };
+        err_t err = netconn_recv(state.nc, &netbuf);
+        if(err != ERR_OK) {
+            printf("DHCP Server Error: Failed to receive DHCP packet. err=%d\r\n", err);
+            continue;
+        }
+
+        ip_addr_t received_ip;
+        u16_t port;
+        netconn_addr(state.nc, &received_ip, &port);
+
+        if(netbuf_len(netbuf) < offsetof(struct dhcp_msg, options)) {
+            /* too short to be a valid DHCP client message */
+            netbuf_delete(netbuf);
+            continue;
+        }
+        if(netbuf_len(netbuf) >= sizeof(struct dhcp_msg)) {
+           printf("DHCP Server Warning: Client sent more options than we know how to parse. len=%d\r\n", netbuf_len(netbuf));
+        }
+
+        //netconn_connect(nc, netbuf_fromaddr(netbuf), netbuf_fromport(netbuf));
+        netbuf_copy(netbuf, &received, sizeof(struct dhcp_msg));
+        netbuf_delete(netbuf);
+
+        uint8_t *message_type = find_dhcp_option(&received, DHCP_OPTION_MESSAGE_TYPE,
+                                                 DHCP_OPTION_MESSAGE_TYPE_LEN, NULL);
+        if(!message_type) {
+            printf("DHCP Server Error: No message type field found");
+            continue;
+        }
+        switch(*message_type) {
+        case DHCP_DISCOVER:
+            handle_dhcp_discover(&state, &received);
+            break;
+        case DHCP_REQUEST:
+            handle_dhcp_request(&state, &received);
+            break;
+        default:
+            printf("DHCP Server Error: Unsupported message type %d\r\n", *message_type);
+            break;
+        }
+    }
+}
+
+static void handle_dhcp_discover(server_state_t *state, struct dhcp_msg *dhcpmsg)
+{
+    if(dhcpmsg->htype != DHCP_HTYPE_ETH)
+        return;
+    if(dhcpmsg->hlen > NETIF_MAX_HWADDR_LEN)
+        return;
+
+    dhcp_lease_t *freelease = find_lease_slot(state->leases, dhcpmsg->chaddr);
+    if(!freelease) {
+        printf("DHCP Server: All leases taken.\r\n");
+        return; /* Nothing available, so do nothing */
+    }
+
+    /* Reuse the DISCOVER buffer for the OFFER response */
+    dhcpmsg->op = DHCP_BOOTREPLY;
+    bzero(dhcpmsg->options, DHCP_OPTIONS_LEN);
+
+    DHCPSERVER_FIRST_CLIENT_IP(&(dhcpmsg->yiaddr));
+    ip4_addr4(&(dhcpmsg->yiaddr)) += (freelease - state->leases);
+
+    uint8_t *opt = (uint8_t *)&dhcpmsg->options;
+    opt = add_dhcp_option_byte(opt, DHCP_OPTION_MESSAGE_TYPE, DHCP_OFFER);
+
+    opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SERVER_ID, &state->server_if->ip_addr, 4);
+    opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SUBNET_MASK, &state->server_if->netmask, 4);
+    opt = add_dhcp_option_bytes(opt, DHCP_OPTION_END, NULL, 0);
+
+    printf("Sending discover response...\r\n");
+    struct netbuf *netbuf = netbuf_new();
+    netbuf_alloc(netbuf, sizeof(struct dhcp_msg));
+    netbuf_take(netbuf, dhcpmsg, sizeof(struct dhcp_msg));
+    netconn_sendto(state->nc, netbuf, IP_ADDR_BROADCAST, 68);
+    netbuf_delete(netbuf);
+}
+
+static void handle_dhcp_request(server_state_t *state, struct dhcp_msg *dhcpmsg)
+{
+    if(dhcpmsg->htype != DHCP_HTYPE_ETH)
+        return;
+    if(dhcpmsg->hlen > NETIF_MAX_HWADDR_LEN)
+        return;
+
+    ip_addr_t requested_ip;
+    uint8_t *requested_ip_opt = find_dhcp_option(dhcpmsg, DHCP_OPTION_REQUESTED_IP, 4, NULL);
+    if(requested_ip_opt) {
+            memcpy(&requested_ip.addr, requested_ip_opt, 4);
+    } else if(ip_addr_cmp(&requested_ip, IP_ADDR_ANY)) {
+        ip_addr_copy(requested_ip, dhcpmsg->ciaddr);
+    } else {
+        printf("DHCP Server Error: No requested IP\r\n");
+        return;
+    }
+    ip_addr_t first_client_ip;
+    DHCPSERVER_FIRST_CLIENT_IP(&first_client_ip);
+
+    /* Test the first 4 octets match */
+    if(ip4_addr1(&requested_ip) != ip4_addr1(&first_client_ip)
+       || ip4_addr2(&requested_ip) != ip4_addr2(&first_client_ip)
+       || ip4_addr3(&requested_ip) != ip4_addr3(&first_client_ip)) {
+        printf("DHCP Server Error: 0x%08lx Not an allowed IP\r\n", requested_ip.addr);
+        return;
+    }
+    /* Test the last octet is in the MAXCLIENTS range */
+    int16_t octet_offs = ip4_addr4(&requested_ip) - ip4_addr4(&first_client_ip);
+    if(octet_offs < 0 || octet_offs >= DHCPSERVER_MAXCLIENTS) {
+        printf("DHCP Server Error: Address out of range\r\n");
+        return;
+    }
+
+    dhcp_lease_t *requested_lease = state->leases + octet_offs;
+    if(requested_lease->expires != 0 && memcmp(requested_lease->hwaddr, dhcpmsg->chaddr,dhcpmsg->hlen))
+    {
+        printf("DHCP Server Error: Lease for address already taken\r\n");
+        return;
+    }
+
+    memcpy(requested_lease->hwaddr, dhcpmsg->chaddr, dhcpmsg->hlen);
+    printf("DHCP lease addr 0x%08lx assigned to MAC %02x:%02x:%02x:%02x:%02x:%02x\r\n", requested_ip.addr, requested_lease->hwaddr[0],
+           requested_lease->hwaddr[1], requested_lease->hwaddr[2], requested_lease->hwaddr[3], requested_lease->hwaddr[4],
+           requested_lease->hwaddr[5]);
+    requested_lease->expires = 1;
+
+    /* Reuse the REQUEST message as the ACK message */
+    dhcpmsg->op = DHCP_BOOTREPLY;
+    bzero(dhcpmsg->options, DHCP_OPTIONS_LEN);
+
+    ip_addr_copy(dhcpmsg->yiaddr, requested_ip);
+
+    uint8_t *opt = (uint8_t *)&dhcpmsg->options;
+    opt = add_dhcp_option_byte(opt, DHCP_OPTION_MESSAGE_TYPE, DHCP_ACK);
+    uint32_t expiry = htonl(DHCPSERVER_LEASE_TIME);
+    opt = add_dhcp_option_bytes(opt, DHCP_OPTION_LEASE_TIME, &expiry, 4);
+    opt = add_dhcp_option_bytes(opt, DHCP_OPTION_SERVER_ID, &state->server_if->ip_addr, 4);
+    opt = add_dhcp_option_bytes(opt, DHCP_OPTION_END, NULL, 0);
+
+    struct netbuf *netbuf = netbuf_new();
+    netbuf_alloc(netbuf, sizeof(struct dhcp_msg));
+    netbuf_take(netbuf, dhcpmsg, sizeof(struct dhcp_msg));
+    netconn_sendto(state->nc, netbuf, IP_ADDR_BROADCAST, 68);
+    netbuf_delete(netbuf);
+}
+
+static uint8_t *find_dhcp_option(struct dhcp_msg *msg, uint8_t option_num, uint8_t min_length, uint8_t *length)
+{
+    uint8_t *start = (uint8_t *)&msg->options;
+    uint8_t *msg_end = (uint8_t *)msg + sizeof(struct dhcp_msg);
+
+    for(uint8_t *p = start; p < msg_end-2;) {
+        uint8_t type = *p++;
+        uint8_t len = *p++;
+        if(type == DHCP_OPTION_END)
+            return NULL;
+        if(p+len >= msg_end)
+            break; /* We've overrun our valid DHCP message size, or this isn't a valid option */
+        if(type == option_num) {
+            if(len < min_length)
+                break;
+            if(length)
+                *length = len;
+            return p; /* start of actual option data */
+        }
+        p += len;
+    }
+    return NULL; /* Not found */
+}
+
+static uint8_t *add_dhcp_option_byte(uint8_t *opt, uint8_t type, uint8_t value)
+{
+    *opt++ = type;
+    *opt++ = 1;
+    *opt++ = value;
+    return opt;
+}
+
+static uint8_t *add_dhcp_option_bytes(uint8_t *opt, uint8_t type, void *value, uint8_t len)
+{
+    *opt++ = type;
+    if(len) {
+        *opt++ = len;
+        memcpy(opt, value, len);
+    }
+    return opt+len;
+}
+
+/* Find a free DHCP lease, or a lease already assigned to 'hwaddr' */
+static dhcp_lease_t *find_lease_slot(dhcp_lease_t *leases, uint8_t *hwaddr)
+{
+    dhcp_lease_t *empty_lease = NULL;
+    for(int i = 0; i < DHCPSERVER_MAXCLIENTS; i++) {
+        if(leases->expires == 0 && !empty_lease)
+            empty_lease = &leases[i];
+        else if (memcmp(hwaddr, leases[i].hwaddr, 6) == 0)
+            return &leases[i];
+
+    }
+    return empty_lease;
+}
+
+static xTaskHandle dhcpserver_task_handle;
+
+void dhcpserver_start(void)
+{
+    xTaskCreate(dhcpserver_task, (signed char *)"DHCPServer", 768, NULL, 8, &dhcpserver_task_handle);
+}
+
+void dhcpserver_stop(void)
+{
+    if(dhcpserver_task_handle) {
+        vTaskDelete(dhcpserver_task_handle);
+        dhcpserver_task_handle = NULL;
+    }
+}

extras/dhcpserver/include/dhcpserver.h

@@ -0,0 +1,34 @@
+/* Very basic LWIP & FreeRTOS-based DHCP server
+
+ */
+#ifndef _DHCPSERVER_H
+#define _DHCPSERVER_H
+
+#ifndef DHCPSERVER_MAXCLIENTS
+#define DHCPSERVER_MAXCLIENTS 4
+#endif
+
+/* First client IP to hand out.
+
+   IP assignment routine is very simple - Fourth octet in IP will be incremented
+   from this value to (value+DHCPSERVER_MAXCLIENTS-1).
+*/
+#ifndef DHCPSERVER_FIRST_CLIENT_IP
+#define DHCPSERVER_FIRST_CLIENT_IP(DST) IP4_ADDR(DST, 192, 168, 3, 5)
+#endif
+
+#ifndef DHCPSERVER_LEASE_TIME
+#define DHCPSERVER_LEASE_TIME 30
+#endif
+
+/* Start DHCP server.
+
+   Static IP of server should already be set and network interface enabled.
+*/
+void dhcpserver_start(void);
+
+/* Stop DHCP server.
+ */
+void dhcpserver_stop(void);
+
+#endif