[NETFILTER]: nf_conntrack_sip: support method specific request/response handling

Add support for per-method request/response handlers and perform SDP
parsing for INVITE/UPDATE requests and for all informational and
successful responses.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 117 insertions, 10 deletions

diff --git a/include/linux/netfilter/nf_conntrack_sip.h b/include/linux/netfilter/nf_conntrack_sip.h
index 68a0d6a41733..da93e80804c2 100644
--- a/include/linux/netfilter/nf_conntrack_sip.h
+++ b/include/linux/netfilter/nf_conntrack_sip.h
@@ -5,6 +5,25 @@
 #define SIP_PORT        5060
 #define SIP_TIMEOUT     3600
 
+struct sip_handler {
+        const char      *method;
+        unsigned int    len;
+        int             (*request)(struct sk_buff *skb,
+                                   const char **dptr, unsigned int *datalen,
+                                   unsigned int cseq);
+        int             (*response)(struct sk_buff *skb,
+                                    const char **dptr, unsigned int *datalen,
+                                    unsigned int cseq, unsigned int code);
+};
+
+#define SIP_HANDLER(__method, __request, __response)                    \
+{                                                                       \
+        .method         = (__method),                                   \
+        .len            = sizeof(__method) - 1,                         \
+        .request        = (__request),                                  \
+        .response       = (__response),                                 \
+}
+
 struct sip_header {
         const char      *name;
         const char      *cname;
@@ -35,6 +54,7 @@ struct sip_header {
         __SIP_HDR(__name, NULL, __search, __match)
 
 enum sip_header_types {
+        SIP_HDR_CSEQ,
         SIP_HDR_FROM,
         SIP_HDR_TO,
         SIP_HDR_CONTACT,
diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index 96bedb52bd4b..1be949febab7 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -212,6 +212,7 @@ EXPORT_SYMBOL_GPL(ct_sip_parse_request);
  * equivalent to multiple headers.
  */
 static const struct sip_header ct_sip_hdrs[] = {
+        [SIP_HDR_CSEQ]                  = SIP_HDR("CSeq", NULL, NULL, digits_len),
         [SIP_HDR_FROM]                  = SIP_HDR("From", "f", "sip:", skp_epaddr_len),
         [SIP_HDR_TO]                    = SIP_HDR("To", "t", "sip:", skp_epaddr_len),
         [SIP_HDR_CONTACT]               = SIP_HDR("Contact", "m", "sip:", skp_epaddr_len),
@@ -566,7 +567,8 @@ static int set_expected_rtp(struct sk_buff *skb,
 }
 
 static int process_sdp(struct sk_buff *skb,
-                       const char **dptr, unsigned int *datalen)
+                       const char **dptr, unsigned int *datalen,
+                       unsigned int cseq)
 {
         enum ip_conntrack_info ctinfo;
         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
@@ -600,6 +602,96 @@ static int process_sdp(struct sk_buff *skb,
 
         return set_expected_rtp(skb, dptr, datalen, &addr, htons(port));
 }
+static int process_invite_response(struct sk_buff *skb,
+                                   const char **dptr, unsigned int *datalen,
+                                   unsigned int cseq, unsigned int code)
+{
+        if ((code >= 100 && code <= 199) ||
+            (code >= 200 && code <= 299))
+                return process_sdp(skb, dptr, datalen, cseq);
+
+        return NF_ACCEPT;
+}
+
+static int process_update_response(struct sk_buff *skb,
+                                   const char **dptr, unsigned int *datalen,
+                                   unsigned int cseq, unsigned int code)
+{
+        if ((code >= 100 && code <= 199) ||
+            (code >= 200 && code <= 299))
+                return process_sdp(skb, dptr, datalen, cseq);
+
+        return NF_ACCEPT;
+}
+
+static const struct sip_handler sip_handlers[] = {
+        SIP_HANDLER("INVITE", process_sdp, process_invite_response),
+        SIP_HANDLER("UPDATE", process_sdp, process_update_response),
+};
+
+static int process_sip_response(struct sk_buff *skb,
+                                const char **dptr, unsigned int *datalen)
+{
+        static const struct sip_handler *handler;
+        enum ip_conntrack_info ctinfo;
+        struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
+        unsigned int matchoff, matchlen;
+        unsigned int code, cseq, dataoff, i;
+
+        if (*datalen < strlen("SIP/2.0 200"))
+                return NF_ACCEPT;
+        code = simple_strtoul(*dptr + strlen("SIP/2.0 "), NULL, 10);
+        if (!code)
+                return NF_DROP;
+
+        if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CSEQ,
+                              &matchoff, &matchlen) <= 0)
+                return NF_DROP;
+        cseq = simple_strtoul(*dptr + matchoff, NULL, 10);
+        if (!cseq)
+                return NF_DROP;
+        dataoff = matchoff + matchlen + 1;
+
+        for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) {
+                handler = &sip_handlers[i];
+                if (handler->response == NULL)
+                        continue;
+                if (*datalen < dataoff + handler->len ||
+                    strnicmp(*dptr + dataoff, handler->method, handler->len))
+                        continue;
+                return handler->response(skb, dptr, datalen, cseq, code);
+        }
+        return NF_ACCEPT;
+}
+
+static int process_sip_request(struct sk_buff *skb,
+                               const char **dptr, unsigned int *datalen)
+{
+        static const struct sip_handler *handler;
+        enum ip_conntrack_info ctinfo;
+        struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
+        unsigned int matchoff, matchlen;
+        unsigned int cseq, i;
+
+        for (i = 0; i < ARRAY_SIZE(sip_handlers); i++) {
+                handler = &sip_handlers[i];
+                if (handler->request == NULL)
+                        continue;
+                if (*datalen < handler->len ||
+                    strnicmp(*dptr, handler->method, handler->len))
+                        continue;
+
+                if (ct_sip_get_header(ct, *dptr, 0, *datalen, SIP_HDR_CSEQ,
+                                      &matchoff, &matchlen) <= 0)
+                        return NF_DROP;
+                cseq = simple_strtoul(*dptr + matchoff, NULL, 10);
+                if (!cseq)
+                        return NF_DROP;
+
+                return handler->request(skb, dptr, datalen, cseq);
+        }
+        return NF_ACCEPT;
+}
 
 static int sip_help(struct sk_buff *skb,
                     unsigned int protoff,
@@ -634,15 +726,10 @@ static int sip_help(struct sk_buff *skb,
         if (datalen < strlen("SIP/2.0 200"))
                 return NF_ACCEPT;
 
-        /* RTP info only in some SDP pkts */
-        if (strnicmp(dptr, "INVITE", strlen("INVITE")) != 0 &&
-            strnicmp(dptr, "UPDATE", strlen("UPDATE")) != 0 &&
-            strnicmp(dptr, "SIP/2.0 180", strlen("SIP/2.0 180")) != 0 &&
-            strnicmp(dptr, "SIP/2.0 183", strlen("SIP/2.0 183")) != 0 &&
-            strnicmp(dptr, "SIP/2.0 200", strlen("SIP/2.0 200")) != 0)
-                return NF_ACCEPT;
-
-        return process_sdp(skb, &dptr, &datalen);
+        if (strnicmp(dptr, "SIP/2.0 ", strlen("SIP/2.0 ")) != 0)
+                return process_sip_request(skb, &dptr, &datalen);
+        else
+                return process_sip_response(skb, &dptr, &datalen);
 }
 
 static struct nf_conntrack_helper sip[MAX_PORTS][2] __read_mostly;