From ae5b7d8ba2c28d7d9835856fe0ca5f6ec95ea768 Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Mon, 29 May 2006 18:27:09 -0700 Subject: [NETFILTER]: Add SIP connection tracking helper Add SIP connection tracking helper. Originally written by Christian Hentschel , some cleanup, minor fixes and bidirectional SIP support added by myself. Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- include/linux/netfilter_ipv4/ip_conntrack_sip.h | 44 +++ net/ipv4/netfilter/Kconfig | 18 + net/ipv4/netfilter/Makefile | 2 + net/ipv4/netfilter/ip_conntrack_sip.c | 471 ++++++++++++++++++++++++ net/ipv4/netfilter/ip_nat_sip.c | 249 +++++++++++++ 5 files changed, 784 insertions(+) create mode 100644 include/linux/netfilter_ipv4/ip_conntrack_sip.h create mode 100644 net/ipv4/netfilter/ip_conntrack_sip.c create mode 100644 net/ipv4/netfilter/ip_nat_sip.c diff --git a/include/linux/netfilter_ipv4/ip_conntrack_sip.h b/include/linux/netfilter_ipv4/ip_conntrack_sip.h new file mode 100644 index 000000000000..913dad66c0fb --- /dev/null +++ b/include/linux/netfilter_ipv4/ip_conntrack_sip.h @@ -0,0 +1,44 @@ +#ifndef __IP_CONNTRACK_SIP_H__ +#define __IP_CONNTRACK_SIP_H__ +#ifdef __KERNEL__ + +#define SIP_PORT 5060 +#define SIP_TIMEOUT 3600 + +#define POS_VIA 0 +#define POS_CONTACT 1 +#define POS_CONTENT 2 +#define POS_MEDIA 3 +#define POS_OWNER 4 +#define POS_CONNECTION 5 +#define POS_REQ_HEADER 6 +#define POS_SDP_HEADER 7 + +struct sip_header_nfo { + const char *lname; + const char *sname; + const char *ln_str; + size_t lnlen; + size_t snlen; + size_t ln_strlen; + int (*match_len)(const char *, const char *, int *); +}; + +extern unsigned int (*ip_nat_sip_hook)(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack *ct, + const char **dptr); +extern unsigned int (*ip_nat_sdp_hook)(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack_expect *exp, + const char *dptr); + +extern int ct_sip_get_info(const char *dptr, size_t dlen, + unsigned int *matchoff, + unsigned int *matchlen, + struct sip_header_nfo *hnfo); +extern int ct_sip_lnlen(const char *line, const char *limit); +extern const char *ct_sip_search(const char *needle, const char *haystack, + size_t needle_len, size_t haystack_len); +#endif /* __KERNEL__ */ +#endif /* __IP_CONNTRACK_SIP_H__ */ diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig index f86aeda3a5a0..ff4b118f14a9 100644 --- a/net/ipv4/netfilter/Kconfig +++ b/net/ipv4/netfilter/Kconfig @@ -191,6 +191,18 @@ config IP_NF_H323 If you want to compile it as a module, say 'M' here and read Documentation/modules.txt. If unsure, say 'N'. +config IP_NF_SIP + tristate "SIP protocol support (EXPERIMENTAL)" + depends on IP_NF_CONNTRACK && EXPERIMENTAL + help + SIP is an application-layer control protocol that can establish, + modify, and terminate multimedia sessions (conferences) such as + Internet telephony calls. With the ip_conntrack_sip and + the ip_nat_sip modules you can support the protocol on a connection + tracking/NATing firewall. + + To compile it as a module, choose M here. If unsure, say Y. + config IP_NF_QUEUE tristate "IP Userspace queueing via NETLINK (OBSOLETE)" help @@ -503,6 +515,12 @@ config IP_NF_NAT_H323 default IP_NF_NAT if IP_NF_H323=y default m if IP_NF_H323=m +config IP_NF_NAT_SIP + tristate + depends on IP_NF_IPTABLES!=n && IP_NF_CONNTRACK!=n && IP_NF_NAT!=n + default IP_NF_NAT if IP_NF_SIP=y + default m if IP_NF_SIP=m + # mangle + specific targets config IP_NF_MANGLE tristate "Packet mangling" diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile index 461cb1eb5de7..3ded4a3af59c 100644 --- a/net/ipv4/netfilter/Makefile +++ b/net/ipv4/netfilter/Makefile @@ -31,6 +31,7 @@ obj-$(CONFIG_IP_NF_AMANDA) += ip_conntrack_amanda.o obj-$(CONFIG_IP_NF_TFTP) += ip_conntrack_tftp.o obj-$(CONFIG_IP_NF_FTP) += ip_conntrack_ftp.o obj-$(CONFIG_IP_NF_IRC) += ip_conntrack_irc.o +obj-$(CONFIG_IP_NF_SIP) += ip_conntrack_sip.o obj-$(CONFIG_IP_NF_NETBIOS_NS) += ip_conntrack_netbios_ns.o # NAT helpers @@ -40,6 +41,7 @@ obj-$(CONFIG_IP_NF_NAT_AMANDA) += ip_nat_amanda.o obj-$(CONFIG_IP_NF_NAT_TFTP) += ip_nat_tftp.o obj-$(CONFIG_IP_NF_NAT_FTP) += ip_nat_ftp.o obj-$(CONFIG_IP_NF_NAT_IRC) += ip_nat_irc.o +obj-$(CONFIG_IP_NF_NAT_SIP) += ip_nat_sip.o # generic IP tables obj-$(CONFIG_IP_NF_IPTABLES) += ip_tables.o diff --git a/net/ipv4/netfilter/ip_conntrack_sip.c b/net/ipv4/netfilter/ip_conntrack_sip.c new file mode 100644 index 000000000000..fc87ce0da40d --- /dev/null +++ b/net/ipv4/netfilter/ip_conntrack_sip.c @@ -0,0 +1,471 @@ +/* SIP extension for IP connection tracking. + * + * (C) 2005 by Christian Hentschel + * based on RR's ip_conntrack_ftp.c and other modules. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include + +#if 0 +#define DEBUGP printk +#else +#define DEBUGP(format, args...) +#endif + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Christian Hentschel "); +MODULE_DESCRIPTION("SIP connection tracking helper"); + +#define MAX_PORTS 8 +static unsigned short ports[MAX_PORTS]; +static int ports_c; +module_param_array(ports, ushort, &ports_c, 0400); +MODULE_PARM_DESC(ports, "port numbers of sip servers"); + +static unsigned int sip_timeout = SIP_TIMEOUT; +module_param(sip_timeout, uint, 0600); +MODULE_PARM_DESC(sip_timeout, "timeout for the master SIP session"); + +unsigned int (*ip_nat_sip_hook)(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack *ct, + const char **dptr); +EXPORT_SYMBOL_GPL(ip_nat_sip_hook); + +unsigned int (*ip_nat_sdp_hook)(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack_expect *exp, + const char *dptr); +EXPORT_SYMBOL_GPL(ip_nat_sdp_hook); + +int ct_sip_get_info(const char *dptr, size_t dlen, + unsigned int *matchoff, + unsigned int *matchlen, + struct sip_header_nfo *hnfo); +EXPORT_SYMBOL_GPL(ct_sip_get_info); + + +static int digits_len(const char *dptr, const char *limit, int *shift); +static int epaddr_len(const char *dptr, const char *limit, int *shift); +static int skp_digits_len(const char *dptr, const char *limit, int *shift); +static int skp_epaddr_len(const char *dptr, const char *limit, int *shift); + +struct sip_header_nfo ct_sip_hdrs[] = { + { /* Via header */ + .lname = "Via:", + .lnlen = sizeof("Via:") - 1, + .sname = "\r\nv:", + .snlen = sizeof("\r\nv:") - 1, /* rfc3261 "\r\n" */ + .ln_str = "UDP ", + .ln_strlen = sizeof("UDP ") - 1, + .match_len = epaddr_len, + }, + { /* Contact header */ + .lname = "Contact:", + .lnlen = sizeof("Contact:") - 1, + .sname = "\r\nm:", + .snlen = sizeof("\r\nm:") - 1, + .ln_str = "sip:", + .ln_strlen = sizeof("sip:") - 1, + .match_len = skp_epaddr_len + }, + { /* Content length header */ + .lname = "Content-Length:", + .lnlen = sizeof("Content-Length:") - 1, + .sname = "\r\nl:", + .snlen = sizeof("\r\nl:") - 1, + .ln_str = ":", + .ln_strlen = sizeof(":") - 1, + .match_len = skp_digits_len + }, + { /* SDP media info */ + .lname = "\nm=", + .lnlen = sizeof("\nm=") - 1, + .sname = "\rm=", + .snlen = sizeof("\rm=") - 1, + .ln_str = "audio ", + .ln_strlen = sizeof("audio ") - 1, + .match_len = digits_len + }, + { /* SDP owner address*/ + .lname = "\no=", + .lnlen = sizeof("\no=") - 1, + .sname = "\ro=", + .snlen = sizeof("\ro=") - 1, + .ln_str = "IN IP4 ", + .ln_strlen = sizeof("IN IP4 ") - 1, + .match_len = epaddr_len + }, + { /* SDP connection info */ + .lname = "\nc=", + .lnlen = sizeof("\nc=") - 1, + .sname = "\rc=", + .snlen = sizeof("\rc=") - 1, + .ln_str = "IN IP4 ", + .ln_strlen = sizeof("IN IP4 ") - 1, + .match_len = epaddr_len + }, + { /* Requests headers */ + .lname = "sip:", + .lnlen = sizeof("sip:") - 1, + .sname = "sip:", + .snlen = sizeof("sip:") - 1, /* yes, i know.. ;) */ + .ln_str = "@", + .ln_strlen = sizeof("@") - 1, + .match_len = epaddr_len + }, + { /* SDP version header */ + .lname = "\nv=", + .lnlen = sizeof("\nv=") - 1, + .sname = "\rv=", + .snlen = sizeof("\rv=") - 1, + .ln_str = "=", + .ln_strlen = sizeof("=") - 1, + .match_len = digits_len + } +}; +EXPORT_SYMBOL_GPL(ct_sip_hdrs); + +/* get line lenght until first CR or LF seen. */ +int ct_sip_lnlen(const char *line, const char *limit) +{ + const char *k = line; + + while ((line <= limit) && (*line == '\r' || *line == '\n')) + line++; + + while (line <= limit) { + if (*line == '\r' || *line == '\n') + break; + line++; + } + return line - k; +} +EXPORT_SYMBOL_GPL(ct_sip_lnlen); + +/* Linear string search, case sensitive. */ +const char *ct_sip_search(const char *needle, const char *haystack, + size_t needle_len, size_t haystack_len) +{ + const char *limit = haystack + (haystack_len - needle_len); + + while (haystack <= limit) { + if (memcmp(haystack, needle, needle_len) == 0) + return haystack; + haystack++; + } + return NULL; +} +EXPORT_SYMBOL_GPL(ct_sip_search); + +static int digits_len(const char *dptr, const char *limit, int *shift) +{ + int len = 0; + while (dptr <= limit && isdigit(*dptr)) { + dptr++; + len++; + } + return len; +} + +/* get digits lenght, skiping blank spaces. */ +static int skp_digits_len(const char *dptr, const char *limit, int *shift) +{ + for (; dptr <= limit && *dptr == ' '; dptr++) + (*shift)++; + + return digits_len(dptr, limit, shift); +} + +/* Simple ipaddr parser.. */ +static int parse_ipaddr(const char *cp, const char **endp, + u_int32_t *ipaddr, const char *limit) +{ + unsigned long int val; + int i, digit = 0; + + for (i = 0, *ipaddr = 0; cp <= limit && i < 4; i++) { + digit = 0; + if (!isdigit(*cp)) + break; + + val = simple_strtoul(cp, (char **)&cp, 10); + if (val > 0xFF) + return -1; + + ((u_int8_t *)ipaddr)[i] = val; + digit = 1; + + if (*cp != '.') + break; + cp++; + } + if (!digit) + return -1; + + if (endp) + *endp = cp; + + return 0; +} + +/* skip ip address. returns it lenght. */ +static int epaddr_len(const char *dptr, const char *limit, int *shift) +{ + const char *aux = dptr; + u_int32_t ip; + + if (parse_ipaddr(dptr, &dptr, &ip, limit) < 0) { + DEBUGP("ip: %s parse failed.!\n", dptr); + return 0; + } + + /* Port number */ + if (*dptr == ':') { + dptr++; + dptr += digits_len(dptr, limit, shift); + } + return dptr - aux; +} + +/* get address length, skiping user info. */ +static int skp_epaddr_len(const char *dptr, const char *limit, int *shift) +{ + int s = *shift; + + for (; dptr <= limit && *dptr != '@'; dptr++) + (*shift)++; + + if (*dptr == '@') { + dptr++; + (*shift)++; + } else + *shift = s; + + return epaddr_len(dptr, limit, shift); +} + +/* Returns 0 if not found, -1 error parsing. */ +int ct_sip_get_info(const char *dptr, size_t dlen, + unsigned int *matchoff, + unsigned int *matchlen, + struct sip_header_nfo *hnfo) +{ + const char *limit, *aux, *k = dptr; + int shift = 0; + + limit = dptr + (dlen - hnfo->lnlen); + + while (dptr <= limit) { + if ((strncmp(dptr, hnfo->lname, hnfo->lnlen) != 0) && + (strncmp(dptr, hnfo->sname, hnfo->snlen) != 0)) { + dptr++; + continue; + } + aux = ct_sip_search(hnfo->ln_str, dptr, hnfo->ln_strlen, + ct_sip_lnlen(dptr, limit)); + if (!aux) { + DEBUGP("'%s' not found in '%s'.\n", hnfo->ln_str, + hnfo->lname); + return -1; + } + aux += hnfo->ln_strlen; + + *matchlen = hnfo->match_len(aux, limit, &shift); + if (!*matchlen) + return -1; + + *matchoff = (aux - k) + shift; + + DEBUGP("%s match succeeded! - len: %u\n", hnfo->lname, + *matchlen); + return 1; + } + DEBUGP("%s header not found.\n", hnfo->lname); + return 0; +} + +static int set_expected_rtp(struct sk_buff **pskb, + struct ip_conntrack *ct, + enum ip_conntrack_info ctinfo, + u_int32_t ipaddr, u_int16_t port, + const char *dptr) +{ + struct ip_conntrack_expect *exp; + enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + int ret; + + exp = ip_conntrack_expect_alloc(ct); + if (exp == NULL) + return NF_DROP; + + exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip; + exp->tuple.src.u.udp.port = 0; + exp->tuple.dst.ip = ipaddr; + exp->tuple.dst.u.udp.port = htons(port); + exp->tuple.dst.protonum = IPPROTO_UDP; + + exp->mask.src.ip = 0xFFFFFFFF; + exp->mask.src.u.udp.port = 0; + exp->mask.dst.ip = 0xFFFFFFFF; + exp->mask.dst.u.udp.port = 0xFFFF; + exp->mask.dst.protonum = 0xFF; + + exp->expectfn = NULL; + exp->flags = 0; + + if (ip_nat_sdp_hook) + ret = ip_nat_sdp_hook(pskb, ctinfo, exp, dptr); + else { + if (ip_conntrack_expect_related(exp) != 0) + ret = NF_DROP; + else + ret = NF_ACCEPT; + } + ip_conntrack_expect_put(exp); + + return ret; +} + +static int sip_help(struct sk_buff **pskb, + struct ip_conntrack *ct, + enum ip_conntrack_info ctinfo) +{ + unsigned int dataoff, datalen; + const char *dptr; + int ret = NF_ACCEPT; + int matchoff, matchlen; + u_int32_t ipaddr; + u_int16_t port; + + /* No Data ? */ + dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr); + if (dataoff >= (*pskb)->len) { + DEBUGP("skb->len = %u\n", (*pskb)->len); + return NF_ACCEPT; + } + + ip_ct_refresh(ct, *pskb, sip_timeout * HZ); + + if (!skb_is_nonlinear(*pskb)) + dptr = (*pskb)->data + dataoff; + else { + DEBUGP("Copy of skbuff not supported yet.\n"); + goto out; + } + + if (ip_nat_sip_hook) { + if (!ip_nat_sip_hook(pskb, ctinfo, ct, &dptr)) { + ret = NF_DROP; + goto out; + } + } + + /* After this point NAT, could have mangled skb, so + we need to recalculate payload lenght. */ + datalen = (*pskb)->len - dataoff; + + if (datalen < (sizeof("SIP/2.0 200") - 1)) + goto out; + + /* RTP info only in some SDP pkts */ + if (memcmp(dptr, "INVITE", sizeof("INVITE") - 1) != 0 && + memcmp(dptr, "SIP/2.0 200", sizeof("SIP/2.0 200") - 1) != 0) { + goto out; + } + /* Get ip and port address from SDP packet. */ + if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen, + &ct_sip_hdrs[POS_CONNECTION]) > 0) { + + /* We'll drop only if there are parse problems. */ + if (parse_ipaddr(dptr + matchoff, NULL, &ipaddr, + dptr + datalen) < 0) { + ret = NF_DROP; + goto out; + } + if (ct_sip_get_info(dptr, datalen, &matchoff, &matchlen, + &ct_sip_hdrs[POS_MEDIA]) > 0) { + + port = simple_strtoul(dptr + matchoff, NULL, 10); + if (port < 1024) { + ret = NF_DROP; + goto out; + } + ret = set_expected_rtp(pskb, ct, ctinfo, + ipaddr, port, dptr); + } + } +out: + return ret; +} + +static struct ip_conntrack_helper sip[MAX_PORTS]; +static char sip_names[MAX_PORTS][10]; + +static void fini(void) +{ + int i; + for (i = 0; i < ports_c; i++) { + DEBUGP("unregistering helper for port %d\n", ports[i]); + ip_conntrack_helper_unregister(&sip[i]); + } +} + +static int __init init(void) +{ + int i, ret; + char *tmpname; + + if (ports_c == 0) + ports[ports_c++] = SIP_PORT; + + for (i = 0; i < ports_c; i++) { + /* Create helper structure */ + memset(&sip[i], 0, sizeof(struct ip_conntrack_helper)); + + sip[i].tuple.dst.protonum = IPPROTO_UDP; + sip[i].tuple.src.u.udp.port = htons(ports[i]); + sip[i].mask.src.u.udp.port = 0xFFFF; + sip[i].mask.dst.protonum = 0xFF; + sip[i].max_expected = 1; + sip[i].timeout = 3 * 60; /* 3 minutes */ + sip[i].me = THIS_MODULE; + sip[i].help = sip_help; + + tmpname = &sip_names[i][0]; + if (ports[i] == SIP_PORT) + sprintf(tmpname, "sip"); + else + sprintf(tmpname, "sip-%d", i); + sip[i].name = tmpname; + + DEBUGP("port #%d: %d\n", i, ports[i]); + + ret = ip_conntrack_helper_register(&sip[i]); + if (ret) { + printk("ERROR registering helper for port %d\n", + ports[i]); + fini(); + return ret; + } + } + return 0; +} + +module_init(init); +module_exit(fini); diff --git a/net/ipv4/netfilter/ip_nat_sip.c b/net/ipv4/netfilter/ip_nat_sip.c new file mode 100644 index 000000000000..6ffba63adca2 --- /dev/null +++ b/net/ipv4/netfilter/ip_nat_sip.c @@ -0,0 +1,249 @@ +/* SIP extension for UDP NAT alteration. + * + * (C) 2005 by Christian Hentschel + * based on RR's ip_nat_ftp.c and other modules. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Christian Hentschel "); +MODULE_DESCRIPTION("SIP NAT helper"); + +#if 0 +#define DEBUGP printk +#else +#define DEBUGP(format, args...) +#endif + +extern struct sip_header_nfo ct_sip_hdrs[]; + +static unsigned int mangle_sip_packet(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack *ct, + const char **dptr, size_t dlen, + char *buffer, int bufflen, + struct sip_header_nfo *hnfo) +{ + unsigned int matchlen, matchoff; + + if (ct_sip_get_info(*dptr, dlen, &matchoff, &matchlen, hnfo) <= 0) + return 0; + + if (!ip_nat_mangle_udp_packet(pskb, ct, ctinfo, + matchoff, matchlen, buffer, bufflen)) + return 0; + + /* We need to reload this. Thanks Patrick. */ + *dptr = (*pskb)->data + (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr); + return 1; +} + +static unsigned int ip_nat_sip(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack *ct, + const char **dptr) +{ + enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; + unsigned int bufflen, dataoff; + u_int32_t ip; + u_int16_t port; + + dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr); + + ip = ct->tuplehash[!dir].tuple.dst.ip; + port = ct->tuplehash[!dir].tuple.dst.u.udp.port; + bufflen = sprintf(buffer, "%u.%u.%u.%u:%u", NIPQUAD(ip), ntohs(port)); + + /* short packet ? */ + if (((*pskb)->len - dataoff) < (sizeof("SIP/2.0") - 1)) + return 0; + + /* Basic rules: requests and responses. */ + if (memcmp(*dptr, "SIP/2.0", sizeof("SIP/2.0") - 1) == 0) { + const char *aux; + + if ((ctinfo) < IP_CT_IS_REPLY) { + mangle_sip_packet(pskb, ctinfo, ct, dptr, + (*pskb)->len - dataoff, + buffer, bufflen, + &ct_sip_hdrs[POS_CONTACT]); + return 1; + } + + if (!mangle_sip_packet(pskb, ctinfo, ct, dptr, + (*pskb)->len - dataoff, + buffer, bufflen, &ct_sip_hdrs[POS_VIA])) + return 0; + + /* This search should ignore case, but later.. */ + aux = ct_sip_search("CSeq:", *dptr, sizeof("CSeq:") - 1, + (*pskb)->len - dataoff); + if (!aux) + return 0; + + if (!ct_sip_search("REGISTER", aux, sizeof("REGISTER"), + ct_sip_lnlen(aux, *dptr + (*pskb)->len - dataoff))) + return 1; + + return mangle_sip_packet(pskb, ctinfo, ct, dptr, + (*pskb)->len - dataoff, + buffer, bufflen, + &ct_sip_hdrs[POS_CONTACT]); + } + if ((ctinfo) < IP_CT_IS_REPLY) { + if (!mangle_sip_packet(pskb, ctinfo, ct, dptr, + (*pskb)->len - dataoff, + buffer, bufflen, &ct_sip_hdrs[POS_VIA])) + return 0; + + /* Mangle Contact if exists only. - watch udp_nat_mangle()! */ + mangle_sip_packet(pskb, ctinfo, ct, dptr, (*pskb)->len - dataoff, + buffer, bufflen, &ct_sip_hdrs[POS_CONTACT]); + return 1; + } + /* This mangle requests headers. */ + return mangle_sip_packet(pskb, ctinfo, ct, dptr, + ct_sip_lnlen(*dptr, + *dptr + (*pskb)->len - dataoff), + buffer, bufflen, &ct_sip_hdrs[POS_REQ_HEADER]); +} + +static int mangle_content_len(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack *ct, + const char *dptr) +{ + unsigned int dataoff, matchoff, matchlen; + char buffer[sizeof("65536")]; + int bufflen; + + dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr); + + /* Get actual SDP lenght */ + if (ct_sip_get_info(dptr, (*pskb)->len - dataoff, &matchoff, + &matchlen, &ct_sip_hdrs[POS_SDP_HEADER]) > 0) { + + /* since ct_sip_get_info() give us a pointer passing 'v=' + we need to add 2 bytes in this count. */ + int c_len = (*pskb)->len - dataoff - matchoff + 2; + + /* Now, update SDP lenght */ + if (ct_sip_get_info(dptr, (*pskb)->len - dataoff, &matchoff, + &matchlen, &ct_sip_hdrs[POS_CONTENT]) > 0) { + + bufflen = sprintf(buffer, "%u", c_len); + + return ip_nat_mangle_udp_packet(pskb, ct, ctinfo, + matchoff, matchlen, + buffer, bufflen); + } + } + return 0; +} + +static unsigned int mangle_sdp(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack *ct, + u_int32_t newip, u_int16_t port, + const char *dptr) +{ + char buffer[sizeof("nnn.nnn.nnn.nnn")]; + unsigned int dataoff, bufflen; + + dataoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct udphdr); + + /* Mangle owner and contact info. */ + bufflen = sprintf(buffer, "%u.%u.%u.%u", NIPQUAD(newip)); + if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff, + buffer, bufflen, &ct_sip_hdrs[POS_OWNER])) + return 0; + + if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff, + buffer, bufflen, &ct_sip_hdrs[POS_CONNECTION])) + return 0; + + /* Mangle media port. */ + bufflen = sprintf(buffer, "%u", port); + if (!mangle_sip_packet(pskb, ctinfo, ct, &dptr, (*pskb)->len - dataoff, + buffer, bufflen, &ct_sip_hdrs[POS_MEDIA])) + return 0; + + return mangle_content_len(pskb, ctinfo, ct, dptr); +} + +/* So, this packet has hit the connection tracking matching code. + Mangle it, and change the expectation to match the new version. */ +static unsigned int ip_nat_sdp(struct sk_buff **pskb, + enum ip_conntrack_info ctinfo, + struct ip_conntrack_expect *exp, + const char *dptr) +{ + struct ip_conntrack *ct = exp->master; + enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + u_int32_t newip; + u_int16_t port; + + DEBUGP("ip_nat_sdp():\n"); + + /* Connection will come from reply */ + newip = ct->tuplehash[!dir].tuple.dst.ip; + + exp->tuple.dst.ip = newip; + exp->saved_proto.udp.port = exp->tuple.dst.u.udp.port; + exp->dir = !dir; + + /* When you see the packet, we need to NAT it the same as the + this one. */ + exp->expectfn = ip_nat_follow_master; + + /* Try to get same port: if not, try to change it. */ + for (port = ntohs(exp->saved_proto.udp.port); port != 0; port++) { + exp->tuple.dst.u.udp.port = htons(port); + if (ip_conntrack_expect_related(exp) == 0) + break; + } + + if (port == 0) + return NF_DROP; + + if (!mangle_sdp(pskb, ctinfo, ct, newip, port, dptr)) { + ip_conntrack_unexpect_related(exp); + return NF_DROP; + } + return NF_ACCEPT; +} + +static void __exit fini(void) +{ + ip_nat_sip_hook = NULL; + ip_nat_sdp_hook = NULL; + /* Make sure noone calls it, meanwhile. */ + synchronize_net(); +} + +static int __init init(void) +{ + BUG_ON(ip_nat_sip_hook); + BUG_ON(ip_nat_sdp_hook); + ip_nat_sip_hook = ip_nat_sip; + ip_nat_sdp_hook = ip_nat_sdp; + return 0; +} + +module_init(init); +module_exit(fini); -- cgit v1.2.2