[PATCH v3 resend] netfilter: nf_conntrack_sip: Handle Cisco 7941/7945 IP phones
From: Kevin Cernekee <cernekee@gmail.com>
Date: 2011-05-20 04:41:55
Most SIP devices use a source port of 5060/udp on SIP requests, so the response automatically comes back to port 5060: phone_ip:5060 -> proxy_ip:5060 REGISTER proxy_ip:5060 -> phone_ip:5060 100 Trying The newer Cisco IP phones, however, use a randomly chosen high source port for the SIP request but expect the response on port 5060: phone_ip:49173 -> proxy_ip:5060 REGISTER proxy_ip:5060 -> phone_ip:5060 100 Trying Standard Linux NAT, with or without nf_nat_sip, will send the reply back to port 49173, not 5060: phone_ip:49173 -> proxy_ip:5060 REGISTER proxy_ip:5060 -> phone_ip:49173 100 Trying But the phone is not listening on 49173, so it will never see the reply. This patch modifies nf_*_sip to work around this quirk by extracting the SIP response port from the Via: header, iff the source IP in the packet header matches the source IP in the SIP request. Signed-off-by: Kevin Cernekee <cernekee@gmail.com> Acked-by: Eric Dumazet <redacted> Cc: Patrick McHardy <redacted> --- include/linux/netfilter/nf_conntrack_sip.h | 3 +++ net/ipv4/netfilter/nf_nat_sip.c | 26 +++++++++++++++++++++++--- net/netfilter/nf_conntrack_sip.c | 17 +++++++++++++++++ 3 files changed, 43 insertions(+), 3 deletions(-)
diff --git a/include/linux/netfilter/nf_conntrack_sip.h b/include/linux/netfilter/nf_conntrack_sip.h
index 0ce91d5..feda699 100644
--- a/include/linux/netfilter/nf_conntrack_sip.h
+++ b/include/linux/netfilter/nf_conntrack_sip.h@@ -2,12 +2,15 @@ #define __NF_CONNTRACK_SIP_H__ #ifdef __KERNEL__ +#include <linux/types.h> + #define SIP_PORT 5060 #define SIP_TIMEOUT 3600 struct nf_ct_sip_master { unsigned int register_cseq; unsigned int invite_cseq; + __be16 forced_dport; }; enum sip_expectation_classes {
diff --git a/net/ipv4/netfilter/nf_nat_sip.c b/net/ipv4/netfilter/nf_nat_sip.c
index e40cf78..e5856b0 100644
--- a/net/ipv4/netfilter/nf_nat_sip.c
+++ b/net/ipv4/netfilter/nf_nat_sip.c@@ -73,6 +73,7 @@ static int map_addr(struct sk_buff *skb, unsigned int dataoff, enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + struct nf_conn_help *help = nfct_help(ct); char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; unsigned int buflen; __be32 newaddr;
@@ -85,7 +86,8 @@ static int map_addr(struct sk_buff *skb, unsigned int dataoff, } else if (ct->tuplehash[dir].tuple.dst.u3.ip == addr->ip && ct->tuplehash[dir].tuple.dst.u.udp.port == port) { newaddr = ct->tuplehash[!dir].tuple.src.u3.ip; - newport = ct->tuplehash[!dir].tuple.src.u.udp.port; + newport = help->help.ct_sip_info.forced_dport ? : + ct->tuplehash[!dir].tuple.src.u.udp.port; } else return 1;
@@ -121,6 +123,7 @@ static unsigned int ip_nat_sip(struct sk_buff *skb, unsigned int dataoff, enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + struct nf_conn_help *help = nfct_help(ct); unsigned int coff, matchoff, matchlen; enum sip_header_types hdr; union nf_inet_addr addr;
@@ -229,6 +232,20 @@ next: !map_sip_addr(skb, dataoff, dptr, datalen, SIP_HDR_TO)) return NF_DROP; + /* Mangle destination port for Cisco phones, then fix up checksums */ + if (dir == IP_CT_DIR_REPLY && help->help.ct_sip_info.forced_dport) { + struct udphdr *uh; + + if (!skb_make_writable(skb, skb->len)) + return NF_DROP; + + uh = (struct udphdr *)(skb->data + ip_hdrlen(skb)); + uh->dest = help->help.ct_sip_info.forced_dport; + + if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, 0, 0, NULL, 0)) + return NF_DROP; + } + return NF_ACCEPT; }
@@ -280,8 +297,10 @@ static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff, enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); + struct nf_conn_help *help = nfct_help(ct); __be32 newip; u_int16_t port; + __be16 srcport; char buffer[sizeof("nnn.nnn.nnn.nnn:nnnnn")]; unsigned buflen;
@@ -294,8 +313,9 @@ static unsigned int ip_nat_sip_expect(struct sk_buff *skb, unsigned int dataoff, /* If the signalling port matches the connection's source port in the * original direction, try to use the destination port in the opposite * direction. */ - if (exp->tuple.dst.u.udp.port == - ct->tuplehash[dir].tuple.src.u.udp.port) + srcport = help->help.ct_sip_info.forced_dport ? : + ct->tuplehash[dir].tuple.src.u.udp.port; + if (exp->tuple.dst.u.udp.port == srcport) port = ntohs(ct->tuplehash[!dir].tuple.dst.u.udp.port); else port = ntohs(exp->tuple.dst.u.udp.port);
diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index 237cc19..b0c16b0 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c@@ -1363,8 +1363,25 @@ static int process_sip_request(struct sk_buff *skb, unsigned int dataoff, { enum ip_conntrack_info ctinfo; struct nf_conn *ct = nf_ct_get(skb, &ctinfo); + struct nf_conn_help *help = nfct_help(ct); + enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); unsigned int matchoff, matchlen; unsigned int cseq, i; + union nf_inet_addr addr; + __be16 port; + + /* Many Cisco IP phones use a high source port for SIP requests, but + * listen for the response on port 5060. If we are the local + * router for one of these phones, save the port number from the + * Via: header so that nf_nat_sip can redirect the responses to + * the correct port. + */ + if (ct_sip_parse_header_uri(ct, *dptr, NULL, *datalen, + SIP_HDR_VIA_UDP, NULL, &matchoff, + &matchlen, &addr, &port) > 0 && + port != ct->tuplehash[dir].tuple.src.u.udp.port && + nf_inet_addr_cmp(&addr, &ct->tuplehash[dir].tuple.src.u3)) + help->help.ct_sip_info.forced_dport = port; for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) { const struct sip_handler *handler;
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1.7.5