busybox/networking/udhcp/dhcprelay.c

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/* vi: set sw=4 ts=4: */
/*
* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com>
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*
* Licensed under GPLv2, see file LICENSE in this source tree.
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*
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* DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
* Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
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* Zuercher Hochschule Winterthur,
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* Netbeat AG
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* Upstream has GPL v2 or later
*/
//applet:IF_DHCPRELAY(APPLET(dhcprelay, BB_DIR_USR_SBIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_DHCPRELAY) += dhcprelay.o
//usage:#define dhcprelay_trivial_usage
//usage: "CLIENT_IFACE[,CLIENT_IFACE2]... SERVER_IFACE [SERVER_IP]"
//usage:#define dhcprelay_full_usage "\n\n"
//usage: "Relay DHCP requests between clients and server"
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#include "common.h"
#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)
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/* This list holds information about clients. The xid_* functions manipulate this list. */
struct xid_item {
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unsigned timestamp;
int client;
uint32_t xid;
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struct sockaddr_in ip;
struct xid_item *next;
} FIX_ALIASING;
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#define dhcprelay_xid_list (*(struct xid_item*)bb_common_bufsiz1)
#define INIT_G() do { setup_common_bufsiz(); } while (0)
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static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client)
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{
struct xid_item *item;
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/* create new xid entry */
item = xmalloc(sizeof(struct xid_item));
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/* add xid entry */
item->ip = *ip;
item->xid = xid;
item->client = client;
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item->timestamp = monotonic_sec();
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item->next = dhcprelay_xid_list.next;
dhcprelay_xid_list.next = item;
return item;
}
static void xid_expire(void)
{
struct xid_item *item = dhcprelay_xid_list.next;
struct xid_item *last = &dhcprelay_xid_list;
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unsigned current_time = monotonic_sec();
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while (item != NULL) {
if ((current_time - item->timestamp) > MAX_LIFETIME) {
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last->next = item->next;
free(item);
item = last->next;
} else {
last = item;
item = item->next;
}
}
}
static struct xid_item *xid_find(uint32_t xid)
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{
struct xid_item *item = dhcprelay_xid_list.next;
while (item != NULL) {
if (item->xid == xid) {
break;
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}
item = item->next;
}
return item;
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}
static void xid_del(uint32_t xid)
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{
struct xid_item *item = dhcprelay_xid_list.next;
struct xid_item *last = &dhcprelay_xid_list;
while (item != NULL) {
if (item->xid == xid) {
last->next = item->next;
free(item);
item = last->next;
} else {
last = item;
item = item->next;
}
}
}
/**
* get_dhcp_packet_type - gets the message type of a dhcp packet
* p - pointer to the dhcp packet
* returns the message type on success, -1 otherwise
*/
static int get_dhcp_packet_type(struct dhcp_packet *p)
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{
uint8_t *op;
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/* it must be either a BOOTREQUEST or a BOOTREPLY */
if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
return -1;
/* get message type option */
op = udhcp_get_option(p, DHCP_MESSAGE_TYPE);
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if (op != NULL)
return op[0];
return -1;
}
/**
* make_iface_list - parses client/server interface names
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* returns array
*/
static char **make_iface_list(char **client_and_server_ifaces, int *client_number)
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{
char *s, **iface_list;
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int i, cn;
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/* get number of items */
cn = 2; /* 1 server iface + at least 1 client one */
s = client_and_server_ifaces[0]; /* list of client ifaces */
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while (*s) {
if (*s == ',')
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cn++;
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s++;
}
*client_number = cn;
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/* create vector of pointers */
iface_list = xzalloc(cn * sizeof(iface_list[0]));
iface_list[0] = client_and_server_ifaces[1]; /* server iface */
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i = 1;
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;
}
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}
return iface_list;
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}
/* Creates listen sockets (in fds) bound to client and server ifaces,
* and returns numerically max fd.
*/
static int init_sockets(char **iface_list, int num_clients, int *fds)
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{
int i, n;
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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];
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}
return n;
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}
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)
libbb: reduce the overhead of single parameter bb_error_msg() calls Back in 2007, commit 0c97c9d43707 ("'simple' error message functions by Loic Grenie") introduced bb_simple_perror_msg() to allow for a lower overhead call to bb_perror_msg() when only a string was being printed with no parameters. This saves space for some CPU architectures because it avoids the overhead of a call to a variadic function. However there has never been a simple version of bb_error_msg(), and since 2007 many new calls to bb_perror_msg() have been added that only take a single parameter and so could have been using bb_simple_perror_message(). This changeset introduces 'simple' versions of bb_info_msg(), bb_error_msg(), bb_error_msg_and_die(), bb_herror_msg() and bb_herror_msg_and_die(), and replaces all calls that only take a single parameter, or use something like ("%s", arg), with calls to the corresponding 'simple' version. Since it is likely that single parameter calls to the variadic functions may be accidentally reintroduced in the future a new debugging config option WARN_SIMPLE_MSG has been introduced. This uses some macro magic which will cause any such calls to generate a warning, but this is turned off by default to avoid use of the unpleasant macros in normal circumstances. This is a large changeset due to the number of calls that have been replaced. The only files that contain changes other than simple substitution of function calls are libbb.h, libbb/herror_msg.c, libbb/verror_msg.c and libbb/xfuncs_printf.c. In miscutils/devfsd.c, networking/udhcp/common.h and util-linux/mdev.c additonal macros have been added for logging so that single parameter and multiple parameter logging variants exist. The amount of space saved varies considerably by architecture, and was found to be as follows (for 'defconfig' using GCC 7.4): Arm: -92 bytes MIPS: -52 bytes PPC: -1836 bytes x86_64: -938 bytes Note that for the MIPS architecture only an exception had to be made disabling the 'simple' calls for 'udhcp' (in networking/udhcp/common.h) because it made these files larger on MIPS. Signed-off-by: James Byrne <james.byrne@origamienergy.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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bb_simple_perror_msg("sendto");
return err;
}
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/**
* pass_to_server() - forwards dhcp packets from client to server
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* p - packet to send
* client - number of the client
*/
static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, int *fds,
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struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
{
int type;
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/* check packet_type */
type = get_dhcp_packet_type(p);
if (type != DHCPDISCOVER && type != DHCPREQUEST
&& type != DHCPDECLINE && type != DHCPRELEASE
&& type != DHCPINFORM
) {
return;
}
/* create new xid entry */
xid_add(p->xid, client_addr, client);
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/* 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);
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}
/**
* pass_to_client() - forwards dhcp packets from server to client
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* p - packet to send
*/
static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
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{
int type;
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struct xid_item *item;
/* check xid */
item = xid_find(p->xid);
if (!item) {
return;
}
/* check packet type */
type = get_dhcp_packet_type(p);
if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
return;
}
//TODO: also do it if (p->flags & htons(BROADCAST_FLAG)) is set!
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if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
if (sendto_ip4(fds[item->client], p, packet_len, &item->ip) != 0) {
return; /* send error occurred */
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}
/* remove xid entry */
xid_del(p->xid);
}
int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int dhcprelay_main(int argc UNUSED_PARAM, char **argv)
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{
struct sockaddr_in server_addr;
char **iface_list;
int *fds;
int num_sockets, max_socket;
uint32_t our_nip;
INIT_G();
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] */
if (!argv[1] || !argv[2])
bb_show_usage();
if (argv[3]) {
if (!inet_aton(argv[3], &server_addr.sin_addr))
libbb: reduce the overhead of single parameter bb_error_msg() calls Back in 2007, commit 0c97c9d43707 ("'simple' error message functions by Loic Grenie") introduced bb_simple_perror_msg() to allow for a lower overhead call to bb_perror_msg() when only a string was being printed with no parameters. This saves space for some CPU architectures because it avoids the overhead of a call to a variadic function. However there has never been a simple version of bb_error_msg(), and since 2007 many new calls to bb_perror_msg() have been added that only take a single parameter and so could have been using bb_simple_perror_message(). This changeset introduces 'simple' versions of bb_info_msg(), bb_error_msg(), bb_error_msg_and_die(), bb_herror_msg() and bb_herror_msg_and_die(), and replaces all calls that only take a single parameter, or use something like ("%s", arg), with calls to the corresponding 'simple' version. Since it is likely that single parameter calls to the variadic functions may be accidentally reintroduced in the future a new debugging config option WARN_SIMPLE_MSG has been introduced. This uses some macro magic which will cause any such calls to generate a warning, but this is turned off by default to avoid use of the unpleasant macros in normal circumstances. This is a large changeset due to the number of calls that have been replaced. The only files that contain changes other than simple substitution of function calls are libbb.h, libbb/herror_msg.c, libbb/verror_msg.c and libbb/xfuncs_printf.c. In miscutils/devfsd.c, networking/udhcp/common.h and util-linux/mdev.c additonal macros have been added for logging so that single parameter and multiple parameter logging variants exist. The amount of space saved varies considerably by architecture, and was found to be as follows (for 'defconfig' using GCC 7.4): Arm: -92 bytes MIPS: -52 bytes PPC: -1836 bytes x86_64: -938 bytes Note that for the MIPS architecture only an exception had to be made disabling the 'simple' calls for 'udhcp' (in networking/udhcp/common.h) because it made these files larger on MIPS. Signed-off-by: James Byrne <james.byrne@origamienergy.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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bb_simple_perror_msg_and_die("bad server IP");
}
iface_list = make_iface_list(argv + 1, &num_sockets);
fds = xmalloc(num_sockets * sizeof(fds[0]));
/* Create sockets and bind one to every iface */
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))
return 1;
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/* Main loop */
while (1) {
// reinit stuff from time to time? go back to make_iface_list
// every N minutes?
fd_set rfds;
struct timeval tv;
int i;
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FD_ZERO(&rfds);
for (i = 0; i < num_sockets; i++)
FD_SET(fds[i], &rfds);
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;
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/* server */
if (FD_ISSET(fds[0], &rfds)) {
packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
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if (packlen > 0) {
pass_to_client(&dhcp_msg, packlen, fds);
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}
}
/* clients */
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for (i = 1; i < num_sockets; i++) {
struct sockaddr_in client_addr;
socklen_t addr_size;
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if (!FD_ISSET(fds[i], &rfds))
continue;
addr_size = sizeof(client_addr);
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packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
(struct sockaddr *)(&client_addr), &addr_size);
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if (packlen <= 0)
continue;
/* Get our IP on corresponding client_iface */
// 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 message 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 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);
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}
}
xid_expire();
} /* while (1) */
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/* return 0; - not reached */
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}