diff options
| -rw-r--r-- | networking/udhcp/dhcprelay.c | 189 |
1 files changed, 118 insertions, 71 deletions
diff --git a/networking/udhcp/dhcprelay.c b/networking/udhcp/dhcprelay.c index a2c7f359d..759a4ba03 100644 --- a/networking/udhcp/dhcprelay.c +++ b/networking/udhcp/dhcprelay.c @@ -11,9 +11,12 @@ */ #include "common.h" -#define SERVER_PORT 67 -#define SELECT_TIMEOUT 5 /* select timeout in sec. */ -#define MAX_LIFETIME 2*60 /* lifetime of an xid entry in sec. */ +#define SERVER_PORT 67 + +/* lifetime of an xid entry in sec. */ +#define MAX_LIFETIME 2*60 +/* select timeout in sec. */ +#define SELECT_TIMEOUT (MAX_LIFETIME / 8) /* This list holds information about clients. The xid_* functions manipulate this list. */ struct xid_item { @@ -67,11 +70,11 @@ static struct xid_item *xid_find(uint32_t xid) struct xid_item *item = dhcprelay_xid_list.next; while (item != NULL) { if (item->xid == xid) { - return item; + break; } item = item->next; } - return NULL; + return item; } static void xid_del(uint32_t xid) @@ -110,62 +113,72 @@ static int get_dhcp_packet_type(struct dhcp_packet *p) } /** - * get_client_devices - parses the devices list - * dev_list - comma separated list of devices + * make_iface_list - parses client/server interface names * returns array */ -static char **get_client_devices(char *dev_list, int *client_number) +static char **make_iface_list(char **client_and_server_ifaces, int *client_number) { - char *s, **client_dev; + char *s, **iface_list; int i, cn; - /* copy list */ - dev_list = xstrdup(dev_list); - - /* get number of items, replace ',' with NULs */ - s = dev_list; - cn = 1; + /* get number of items */ + cn = 2; /* 1 server iface + at least 1 client one */ + s = client_and_server_ifaces[0]; /* list of client ifaces */ while (*s) { - if (*s == ',') { - *s = '\0'; + if (*s == ',') cn++; - } s++; } *client_number = cn; /* create vector of pointers */ - client_dev = xzalloc(cn * sizeof(*client_dev)); - client_dev[0] = dev_list; + iface_list = xzalloc(cn * sizeof(iface_list[0])); + + iface_list[0] = client_and_server_ifaces[1]; /* server iface */ + i = 1; - while (i != cn) { - client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1; - i++; + s = xstrdup(client_and_server_ifaces[0]); /* list of client ifaces */ + goto store_client_iface_name; + + while (i < cn) { + if (*s++ == ',') { + s[-1] = '\0'; + store_client_iface_name: + iface_list[i++] = s; + } } - return client_dev; + + return iface_list; } /* Creates listen sockets (in fds) bound to client and server ifaces, * and returns numerically max fd. */ -static int init_sockets(char **client_ifaces, int num_clients, - char *server_iface, int *fds) +static int init_sockets(char **iface_list, int num_clients, int *fds) { int i, n; - /* talk to real server on bootps */ - fds[0] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server_iface); - n = fds[0]; - - for (i = 1; i < num_clients; i++) { - /* listen for clients on bootps */ - fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, client_ifaces[i-1]); - if (fds[i] > n) + n = 0; + for (i = 0; i < num_clients; i++) { + fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, iface_list[i]); + if (n < fds[i]) n = fds[i]; } return n; } +static int sendto_ip4(int sock, const void *msg, int msg_len, struct sockaddr_in *to) +{ + int err; + + errno = 0; + err = sendto(sock, msg, msg_len, 0, (struct sockaddr*) to, sizeof(*to)); + err -= msg_len; + if (err) + bb_perror_msg("sendto"); + return err; +} + /** * pass_to_server() - forwards dhcp packets from client to server * p - packet to send @@ -174,7 +187,7 @@ static int init_sockets(char **client_ifaces, int num_clients, static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, int *fds, struct sockaddr_in *client_addr, struct sockaddr_in *server_addr) { - int res, type; + int type; /* check packet_type */ type = get_dhcp_packet_type(p); @@ -188,13 +201,12 @@ static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, in /* create new xid entry */ xid_add(p->xid, client_addr, client); - /* forward request to LAN (server) */ - errno = 0; - res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr, - sizeof(struct sockaddr_in)); - if (res != packet_len) { - bb_perror_msg("sendto"); - } + /* forward request to server */ + /* note that we send from fds[0] which is bound to SERVER_PORT (67). + * IOW: we send _from_ SERVER_PORT! Although this may look strange, + * RFC 1542 not only allows, but prescribes this for BOOTP relays. + */ + sendto_ip4(fds[0], p, packet_len, server_addr); } /** @@ -203,7 +215,7 @@ static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, in */ static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds) { - int res, type; + int type; struct xid_item *item; /* check xid */ @@ -218,14 +230,12 @@ static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds) return; } +//TODO: also do it if (p->flags & htons(BROADCAST_FLAG)) is set! if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY)) item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST); - errno = 0; - res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*) &(item->ip), - sizeof(item->ip)); - if (res != packet_len) { - bb_perror_msg("sendto"); - return; + + if (sendto_ip4(fds[item->client], p, packet_len, &item->ip) != 0) { + return; /* send error occurred */ } /* remove xid entry */ @@ -235,36 +245,30 @@ static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds) int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int dhcprelay_main(int argc, char **argv) { - struct dhcp_packet dhcp_msg; struct sockaddr_in server_addr; - struct sockaddr_in client_addr; - fd_set rfds; - char **client_ifaces; + char **iface_list; int *fds; int num_sockets, max_socket; uint32_t our_nip; server_addr.sin_family = AF_INET; + server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); server_addr.sin_port = htons(SERVER_PORT); - /* dhcprelay client_iface1,client_iface2,... server_iface [server_IP] */ + /* dhcprelay CLIENT_IFACE1[,CLIENT_IFACE2...] SERVER_IFACE [SERVER_IP] */ if (argc == 4) { if (!inet_aton(argv[3], &server_addr.sin_addr)) bb_perror_msg_and_die("bad server IP"); - } else if (argc == 3) { - server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); - } else { + } else if (argc != 3) { bb_show_usage(); } - /* Produce list of client ifaces */ - client_ifaces = get_client_devices(argv[1], &num_sockets); + iface_list = make_iface_list(argv + 1, &num_sockets); - num_sockets++; /* for server socket at fds[0] */ fds = xmalloc(num_sockets * sizeof(fds[0])); /* Create sockets and bind one to every iface */ - max_socket = init_sockets(client_ifaces, num_sockets, argv[2], fds); + max_socket = init_sockets(iface_list, num_sockets, fds); /* Get our IP on server_iface */ if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL)) @@ -272,11 +276,10 @@ int dhcprelay_main(int argc, char **argv) /* Main loop */ while (1) { -//reinit stuff from time to time? go back to get_client_devices -//every N minutes? +// reinit stuff from time to time? go back to make_iface_list +// every N minutes? + fd_set rfds; struct timeval tv; - size_t packlen; - socklen_t addr_size; int i; FD_ZERO(&rfds); @@ -285,6 +288,9 @@ int dhcprelay_main(int argc, char **argv) tv.tv_sec = SELECT_TIMEOUT; tv.tv_usec = 0; if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) { + int packlen; + struct dhcp_packet dhcp_msg; + /* server */ if (FD_ISSET(fds[0], &rfds)) { packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]); @@ -292,24 +298,65 @@ int dhcprelay_main(int argc, char **argv) pass_to_client(&dhcp_msg, packlen, fds); } } + /* clients */ for (i = 1; i < num_sockets; i++) { + struct sockaddr_in client_addr; + socklen_t addr_size; + if (!FD_ISSET(fds[i], &rfds)) continue; - addr_size = sizeof(struct sockaddr_in); + + addr_size = sizeof(client_addr); packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0, (struct sockaddr *)(&client_addr), &addr_size); if (packlen <= 0) continue; /* Get our IP on corresponding client_iface */ -//why? what if server can't route such IP? - if (udhcp_read_interface(client_ifaces[i-1], NULL, &dhcp_msg.gateway_nip, NULL)) { - /* Fall back to our server_iface's IP */ -//this makes more sense! +// RFC 1542 +// 4.1 General BOOTP Processing for Relay Agents +// 4.1.1 BOOTREQUEST Messages +// If the relay agent does decide to relay the request, it MUST examine +// the 'giaddr' ("gateway" IP address) field. If this field is zero, +// the relay agent MUST fill this field with the IP address of the +// interface on which the request was received. If the interface has +// more than one IP address logically associated with it, the relay +// agent SHOULD choose one IP address associated with that interface and +// use it consistently for all BOOTP messages it relays. If the +// 'giaddr' field contains some non-zero value, the 'giaddr' field MUST +// NOT be modified. The relay agent MUST NOT, under any circumstances, +// fill the 'giaddr' field with a broadcast address as is suggested in +// [1] (Section 8, sixth paragraph). + +// but why? what if server can't route such IP? Client ifaces may be, say, NATed! + +// 4.1.2 BOOTREPLY Messages +// BOOTP relay agents relay BOOTREPLY messages only to BOOTP clients. +// It is the responsibility of BOOTP servers to send BOOTREPLY messages +// directly to the relay agent identified in the 'giaddr' field. +// (yeah right, unless it is impossible... see comment above) +// Therefore, a relay agent may assume that all BOOTREPLY messages it +// receives are intended for BOOTP clients on its directly-connected +// networks. +// +// When a relay agent receives a BOOTREPLY message, it should examine +// the BOOTP 'giaddr', 'yiaddr', 'chaddr', 'htype', and 'hlen' fields. +// These fields should provide adequate information for the relay agent +// to deliver the BOOTREPLY message to the client. +// +// The 'giaddr' field can be used to identify the logical interface from +// which the reply must be sent (i.e., the host or router interface +// connected to the same network as the BOOTP client). If the content +// of the 'giaddr' field does not match one of the relay agent's +// directly-connected logical interfaces, the BOOTREPLY messsage MUST be +// silently discarded. + if (udhcp_read_interface(iface_list[i], NULL, &dhcp_msg.gateway_nip, NULL)) { + /* Fall back to our IP on server iface */ +// this makes more sense! dhcp_msg.gateway_nip = our_nip; } -//maybe set dhcp_msg.flags |= BROADCAST_FLAG too? +// maybe dhcp_msg.hops++? drop packets with too many hops (RFC 1542 says 4 or 16)? pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr); } } |