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dhcprelay: code shrink, and explain its workings a bit more

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function                                             old     new   delta
sendto_ip4                                             -      55     +55
dhcprelay_main                                      1059     942    -117
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/1 up/down: 55/-117)           Total: -62 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2010-10-06 01:45:24 +02:00
parent 28458c64db
commit c0f39b0fb2
1 changed files with 118 additions and 71 deletions
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189
networking/udhcp/dhcprelay.c
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@ -11,9 +11,12 @@
*/ */
#include "common.h" #include "common.h"
#define SERVER_PORT 67 #define SERVER_PORT 67
#define SELECT_TIMEOUT 5 /* select timeout in sec. */
#define MAX_LIFETIME 2*60 /* lifetime of an xid entry in sec. */ /* 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. */ /* This list holds information about clients. The xid_* functions manipulate this list. */
struct xid_item { struct xid_item {
@ -67,11 +70,11 @@ static struct xid_item *xid_find(uint32_t xid)
struct xid_item *item = dhcprelay_xid_list.next; struct xid_item *item = dhcprelay_xid_list.next;
while (item != NULL) { while (item != NULL) {
if (item->xid == xid) { if (item->xid == xid) {
return item; break;
} }
item = item->next; item = item->next;
} }
return NULL; return item;
} }
static void xid_del(uint32_t xid) 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 * make_iface_list - parses client/server interface names
* dev_list - comma separated list of devices
* returns array * 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; int i, cn;
/* copy list */ /* get number of items */
dev_list = xstrdup(dev_list); cn = 2; /* 1 server iface + at least 1 client one */
s = client_and_server_ifaces[0]; /* list of client ifaces */
/* get number of items, replace ',' with NULs */
s = dev_list;
cn = 1;
while (*s) { while (*s) {
if (*s == ',') { if (*s == ',')
*s = '\0';
cn++; cn++;
}
s++; s++;
} }
*client_number = cn; *client_number = cn;
/* create vector of pointers */ /* create vector of pointers */
client_dev = xzalloc(cn * sizeof(*client_dev)); iface_list = xzalloc(cn * sizeof(iface_list[0]));
client_dev[0] = dev_list;
iface_list[0] = client_and_server_ifaces[1]; /* server iface */
i = 1; i = 1;
while (i != cn) { s = xstrdup(client_and_server_ifaces[0]); /* list of client ifaces */
client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1; goto store_client_iface_name;
i++;
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, /* Creates listen sockets (in fds) bound to client and server ifaces,
* and returns numerically max fd. * and returns numerically max fd.
*/ */
static int init_sockets(char **client_ifaces, int num_clients, static int init_sockets(char **iface_list, int num_clients, int *fds)
char *server_iface, int *fds)
{ {
int i, n; int i, n;
/* talk to real server on bootps */ n = 0;
fds[0] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server_iface); for (i = 0; i < num_clients; i++) {
n = fds[0]; fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, iface_list[i]);
if (n < fds[i])
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 = fds[i]; n = fds[i];
} }
return n; 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 * pass_to_server() - forwards dhcp packets from client to server
* p - packet to send * 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, 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) struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
{ {
int res, type; int type;
/* check packet_type */ /* check packet_type */
type = get_dhcp_packet_type(p); 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 */ /* create new xid entry */
xid_add(p->xid, client_addr, client); xid_add(p->xid, client_addr, client);
/* forward request to LAN (server) */ /* forward request to server */
errno = 0; /* note that we send from fds[0] which is bound to SERVER_PORT (67).
res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr, * IOW: we send _from_ SERVER_PORT! Although this may look strange,
sizeof(struct sockaddr_in)); * RFC 1542 not only allows, but prescribes this for BOOTP relays.
if (res != packet_len) { */
bb_perror_msg("sendto"); 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) static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
{ {
int res, type; int type;
struct xid_item *item; struct xid_item *item;
/* check xid */ /* check xid */
@ -218,14 +230,12 @@ static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
return; return;
} }
//TODO: also do it if (p->flags & htons(BROADCAST_FLAG)) is set!
if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY)) if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST); item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
errno = 0;
res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*) &(item->ip), if (sendto_ip4(fds[item->client], p, packet_len, &item->ip) != 0) {
sizeof(item->ip)); return; /* send error occurred */
if (res != packet_len) {
bb_perror_msg("sendto");
return;
} }
/* remove xid entry */ /* 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) MAIN_EXTERNALLY_VISIBLE;
int dhcprelay_main(int argc, char **argv) int dhcprelay_main(int argc, char **argv)
{ {
struct dhcp_packet dhcp_msg;
struct sockaddr_in server_addr; struct sockaddr_in server_addr;
struct sockaddr_in client_addr; char **iface_list;
fd_set rfds;
char **client_ifaces;
int *fds; int *fds;
int num_sockets, max_socket; int num_sockets, max_socket;
uint32_t our_nip; uint32_t our_nip;
server_addr.sin_family = AF_INET; server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
server_addr.sin_port = htons(SERVER_PORT); 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 (argc == 4) {
if (!inet_aton(argv[3], &server_addr.sin_addr)) if (!inet_aton(argv[3], &server_addr.sin_addr))
bb_perror_msg_and_die("bad server IP"); bb_perror_msg_and_die("bad server IP");
} else if (argc == 3) { } else if (argc != 3) {
server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
} else {
bb_show_usage(); bb_show_usage();
} }
/* Produce list of client ifaces */ iface_list = make_iface_list(argv + 1, &num_sockets);
client_ifaces = get_client_devices(argv[1], &num_sockets);
num_sockets++; /* for server socket at fds[0] */
fds = xmalloc(num_sockets * sizeof(fds[0])); fds = xmalloc(num_sockets * sizeof(fds[0]));
/* Create sockets and bind one to every iface */ /* 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 */ /* Get our IP on server_iface */
if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL)) if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL))
@ -272,11 +276,10 @@ int dhcprelay_main(int argc, char **argv)
/* Main loop */ /* Main loop */
while (1) { while (1) {
//reinit stuff from time to time? go back to get_client_devices // reinit stuff from time to time? go back to make_iface_list
//every N minutes? // every N minutes?
fd_set rfds;
struct timeval tv; struct timeval tv;
size_t packlen;
socklen_t addr_size;
int i; int i;
FD_ZERO(&rfds); FD_ZERO(&rfds);
@ -285,6 +288,9 @@ int dhcprelay_main(int argc, char **argv)
tv.tv_sec = SELECT_TIMEOUT; tv.tv_sec = SELECT_TIMEOUT;
tv.tv_usec = 0; tv.tv_usec = 0;
if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) { if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
int packlen;
struct dhcp_packet dhcp_msg;
/* server */ /* server */
if (FD_ISSET(fds[0], &rfds)) { if (FD_ISSET(fds[0], &rfds)) {
packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]); 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); pass_to_client(&dhcp_msg, packlen, fds);
} }
} }
/* clients */ /* clients */
for (i = 1; i < num_sockets; i++) { for (i = 1; i < num_sockets; i++) {
struct sockaddr_in client_addr;
socklen_t addr_size;
if (!FD_ISSET(fds[i], &rfds)) if (!FD_ISSET(fds[i], &rfds))
continue; continue;
addr_size = sizeof(struct sockaddr_in);
addr_size = sizeof(client_addr);
packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0, packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
(struct sockaddr *)(&client_addr), &addr_size); (struct sockaddr *)(&client_addr), &addr_size);
if (packlen <= 0) if (packlen <= 0)
continue; continue;
/* Get our IP on corresponding client_iface */ /* Get our IP on corresponding client_iface */
//why? what if server can't route such IP? // RFC 1542
if (udhcp_read_interface(client_ifaces[i-1], NULL, &dhcp_msg.gateway_nip, NULL)) { // 4.1 General BOOTP Processing for Relay Agents
/* Fall back to our server_iface's IP */ // 4.1.1 BOOTREQUEST Messages
//this makes more sense! // 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; 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); pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
} }
} }