/* * ip_vs_ftp.c: IPVS ftp application module * * Version: $Id: ip_vs_ftp.c,v 1.13 2002/09/15 08:14:08 wensong Exp $ * * Authors: Wensong Zhang <wensong@linuxvirtualserver.org> * * Changes: * * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp. * * IP_MASQ_FTP ftp masquerading module * * Version: @(#)ip_masq_ftp.c 0.04 02/05/96 * * Author: Wouter Gadeyne * */ #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/kernel.h> #include <linux/skbuff.h> #include <linux/in.h> #include <linux/ip.h> #include <net/protocol.h> #include <net/tcp.h> #include <asm/unaligned.h> #include <net/ip_vs.h> #define SERVER_STRING "227 Entering Passive Mode (" #define CLIENT_STRING "PORT " /* * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper * First port is set to the default port. */ static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0}; module_param_array(ports, ushort, NULL, 0); MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands"); /* Dummy variable */ static int ip_vs_ftp_pasv; static int ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp) { return 0; } static int ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp) { return 0; } /* * Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started * with the "pattern" and terminated with the "term" character. * <addr,port> is in network order. */ static int ip_vs_ftp_get_addrport(char *data, char *data_limit, const char *pattern, size_t plen, char term, __be32 *addr, __be16 *port, char **start, char **end) { unsigned char p[6]; int i = 0; if (data_limit - data < plen) { /* check if there is partial match */ if (strnicmp(data, pattern, data_limit - data) == 0) return -1; else return 0; } if (strnicmp(data, pattern, plen) != 0) { return 0; } *start = data + plen; for (data = *start; *data != term; data++) { if (data == data_limit) return -1; } *end = data; memset(p, 0, sizeof(p)); for (data = *start; data != *end; data++) { if (*data >= '0' && *data <= '9') { p[i] = p[i]*10 + *data - '0'; } else if (*data == ',' && i < 5) { i++; } else { /* unexpected character */ return -1; } } if (i != 5) return -1; *addr = get_unaligned((__be32 *)p); *port = get_unaligned((__be16 *)(p + 4)); return 1; } /* * Look at outgoing ftp packets to catch the response to a PASV command * from the server (inside-to-outside). * When we see one, we build a connection entry with the client address, * client port 0 (unknown at the moment), the server address and the * server port. Mark the current connection entry as a control channel * of the new entry. All this work is just to make the data connection * can be scheduled to the right server later. * * The outgoing packet should be something like * "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)". * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number. */ static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp, struct sk_buff **pskb, int *diff) { struct iphdr *iph; struct tcphdr *th; char *data, *data_limit; char *start, *end; __be32 from; __be16 port; struct ip_vs_conn *n_cp; char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */ unsigned buf_len; int ret; *diff = 0; /* Only useful for established sessions */ if (cp->state != IP_VS_TCP_S_ESTABLISHED) return 1; /* Linear packets are much easier to deal with. */ if (!ip_vs_make_skb_writable(pskb, (*pskb)->len)) return 0; if (cp->app_data == &ip_vs_ftp_pasv) { iph = ip_hdr(*pskb); th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]); data = (char *)th + (th->doff << 2); data_limit = skb_tail_pointer(*pskb); if (ip_vs_ftp_get_addrport(data, data_limit, SERVER_STRING, sizeof(SERVER_STRING)-1, ')', &from, &port, &start, &end) != 1) return 1; IP_VS_DBG(7, "PASV response (%u.%u.%u.%u:%d) -> " "%u.%u.%u.%u:%d detected\n", NIPQUAD(from), ntohs(port), NIPQUAD(cp->caddr), 0); /* * Now update or create an connection entry for it */ n_cp = ip_vs_conn_out_get(iph->protocol, from, port, cp->caddr, 0); if (!n_cp) { n_cp = ip_vs_conn_new(IPPROTO_TCP, cp->caddr, 0, cp->vaddr, port, from, port, IP_VS_CONN_F_NO_CPORT, cp->dest); if (!n_cp) return 0; /* add its controller */ ip_vs_control_add(n_cp, cp); } /* * Replace the old passive address with the new one */ from = n_cp->vaddr; port = n_cp->vport; sprintf(buf,"%d,%d,%d,%d,%d,%d", NIPQUAD(from), (ntohs(port)>>8)&255, ntohs(port)&255); buf_len = strlen(buf); /* * Calculate required delta-offset to keep TCP happy */ *diff = buf_len - (end-start); if (*diff == 0) { /* simply replace it with new passive address */ memcpy(start, buf, buf_len); ret = 1; } else { ret = !ip_vs_skb_replace(*pskb, GFP_ATOMIC, start, end-start, buf, buf_len); } cp->app_data = NULL; ip_vs_tcp_conn_listen(n_cp); ip_vs_conn_put(n_cp); return ret; } return 1; } /* * Look at incoming ftp packets to catch the PASV/PORT command * (outside-to-inside). * * The incoming packet having the PORT command should be something like * "PORT xxx,xxx,xxx,xxx,ppp,ppp\n". * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number. * In this case, we create a connection entry using the client address and * port, so that the active ftp data connection from the server can reach * the client. */ static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp, struct sk_buff **pskb, int *diff) { struct iphdr *iph; struct tcphdr *th; char *data, *data_start, *data_limit; char *start, *end; __be32 to; __be16 port; struct ip_vs_conn *n_cp; /* no diff required for incoming packets */ *diff = 0; /* Only useful for established sessions */ if (cp->state != IP_VS_TCP_S_ESTABLISHED) return 1; /* Linear packets are much easier to deal with. */ if (!ip_vs_make_skb_writable(pskb, (*pskb)->len)) return 0; /* * Detecting whether it is passive */ iph = ip_hdr(*pskb); th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]); /* Since there may be OPTIONS in the TCP packet and the HLEN is the length of the header in 32-bit multiples, it is accurate to calculate data address by th+HLEN*4 */ data = data_start = (char *)th + (th->doff << 2); data_limit = skb_tail_pointer(*pskb); while (data <= data_limit - 6) { if (strnicmp(data, "PASV\r\n", 6) == 0) { /* Passive mode on */ IP_VS_DBG(7, "got PASV at %td of %td\n", data - data_start, data_limit - data_start); cp->app_data = &ip_vs_ftp_pasv; return 1; } data++; } /* * To support virtual FTP server, the scenerio is as follows: * FTP client ----> Load Balancer ----> FTP server * First detect the port number in the application data, * then create a new connection entry for the coming data * connection. */ if (ip_vs_ftp_get_addrport(data_start, data_limit, CLIENT_STRING, sizeof(CLIENT_STRING)-1, '\r', &to, &port, &start, &end) != 1) return 1; IP_VS_DBG(7, "PORT %u.%u.%u.%u:%d detected\n", NIPQUAD(to), ntohs(port)); /* Passive mode off */ cp->app_data = NULL; /* * Now update or create a connection entry for it */ IP_VS_DBG(7, "protocol %s %u.%u.%u.%u:%d %u.%u.%u.%u:%d\n", ip_vs_proto_name(iph->protocol), NIPQUAD(to), ntohs(port), NIPQUAD(cp->vaddr), 0); n_cp = ip_vs_conn_in_get(iph->protocol, to, port, cp->vaddr, htons(ntohs(cp->vport)-1)); if (!n_cp) { n_cp = ip_vs_conn_new(IPPROTO_TCP, to, port, cp->vaddr, htons(ntohs(cp->vport)-1), cp->daddr, htons(ntohs(cp->dport)-1), 0, cp->dest); if (!n_cp) return 0; /* add its controller */ ip_vs_control_add(n_cp, cp); } /* * Move tunnel to listen state */ ip_vs_tcp_conn_listen(n_cp); ip_vs_conn_put(n_cp); return 1; } static struct ip_vs_app ip_vs_ftp = { .name = "ftp", .type = IP_VS_APP_TYPE_FTP, .protocol = IPPROTO_TCP, .module = THIS_MODULE, .incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list), .init_conn = ip_vs_ftp_init_conn, .done_conn = ip_vs_ftp_done_conn, .bind_conn = NULL, .unbind_conn = NULL, .pkt_out = ip_vs_ftp_out, .pkt_in = ip_vs_ftp_in, }; /* * ip_vs_ftp initialization */ static int __init ip_vs_ftp_init(void) { int i, ret; struct ip_vs_app *app = &ip_vs_ftp; ret = register_ip_vs_app(app); if (ret) return ret; for (i=0; i<IP_VS_APP_MAX_PORTS; i++) { if (!ports[i]) continue; ret = register_ip_vs_app_inc(app, app->protocol, ports[i]); if (ret) break; IP_VS_INFO("%s: loaded support on port[%d] = %d\n", app->name, i, ports[i]); } if (ret) unregister_ip_vs_app(app); return ret; } /* * ip_vs_ftp finish. */ static void __exit ip_vs_ftp_exit(void) { unregister_ip_vs_app(&ip_vs_ftp); } module_init(ip_vs_ftp_init); module_exit(ip_vs_ftp_exit); MODULE_LICENSE("GPL");