[NETFILTER]: nf_conntrack_sip: introduce SIP-URI parsing helper

Introduce a helper function to parse a SIP-URI in a header value, optionally
iterating through all headers of this kind.

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

2 files changed, 112 insertions, 0 deletions

diff --git a/include/linux/netfilter/nf_conntrack_sip.h b/include/linux/netfilter/nf_conntrack_sip.h
index ccc701422963..87bc6f79efc4 100644
--- a/include/linux/netfilter/nf_conntrack_sip.h
+++ b/include/linux/netfilter/nf_conntrack_sip.h
@@ -67,6 +67,11 @@ extern int ct_sip_get_header(const struct nf_conn *ct, const char *dptr,
                              unsigned int dataoff, unsigned int datalen,
                              enum sip_header_types type,
                              unsigned int *matchoff, unsigned int *matchlen);
+extern int ct_sip_parse_header_uri(const struct nf_conn *ct, const char *dptr,
+                                   unsigned int *dataoff, unsigned int datalen,
+                                   enum sip_header_types type, int *in_header,
+                                   unsigned int *matchoff, unsigned int *matchlen,
+                                   union nf_inet_addr *addr, __be16 *port);
 
 extern int ct_sip_get_sdp_header(const struct nf_conn *ct, const char *dptr,
                                  unsigned int dataoff, unsigned int datalen,
diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index cbc91598acee..a74d76a97312 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -190,6 +190,9 @@ EXPORT_SYMBOL_GPL(ct_sip_parse_request);
  * whitespace and the values. Whitespace in this context means any amount of
  * tabs, spaces and continuation lines, which are treated as a single whitespace
  * character.
+ *
+ * Some headers may appear multiple times. A comma seperated list of values is
+ * equivalent to multiple headers.
  */
 static const struct sip_header ct_sip_hdrs[] = {
         [SIP_HDR_FROM]                  = SIP_HDR("From", "f", "sip:", skp_epaddr_len),
@@ -322,6 +325,110 @@ int ct_sip_get_header(const struct nf_conn *ct, const char *dptr,
 }
 EXPORT_SYMBOL_GPL(ct_sip_get_header);
 
+/* Get next header field in a list of comma seperated values */
+static int ct_sip_next_header(const struct nf_conn *ct, const char *dptr,
+                              unsigned int dataoff, unsigned int datalen,
+                              enum sip_header_types type,
+                              unsigned int *matchoff, unsigned int *matchlen)
+{
+        const struct sip_header *hdr = &ct_sip_hdrs[type];
+        const char *start = dptr, *limit = dptr + datalen;
+        int shift = 0;
+
+        dptr += dataoff;
+
+        dptr = ct_sip_header_search(dptr, limit, ",", strlen(","));
+        if (!dptr)
+                return 0;
+
+        dptr = ct_sip_header_search(dptr, limit, hdr->search, hdr->slen);
+        if (!dptr)
+                return 0;
+        dptr += hdr->slen;
+
+        *matchoff = dptr - start;
+        *matchlen = hdr->match_len(ct, dptr, limit, &shift);
+        if (!*matchlen)
+                return -1;
+        *matchoff += shift;
+        return 1;
+}
+
+/* Walk through headers until a parsable one is found or no header of the
+ * given type is left. */
+static int ct_sip_walk_headers(const struct nf_conn *ct, const char *dptr,
+                               unsigned int dataoff, unsigned int datalen,
+                               enum sip_header_types type, int *in_header,
+                               unsigned int *matchoff, unsigned int *matchlen)
+{
+        int ret;
+
+        if (in_header && *in_header) {
+                while (1) {
+                        ret = ct_sip_next_header(ct, dptr, dataoff, datalen,
+                                                 type, matchoff, matchlen);
+                        if (ret > 0)
+                                return ret;
+                        if (ret == 0)
+                                break;
+                        dataoff += *matchoff;
+                }
+                *in_header = 0;
+        }
+
+        while (1) {
+                ret = ct_sip_get_header(ct, dptr, dataoff, datalen,
+                                        type, matchoff, matchlen);
+                if (ret > 0)
+                        break;
+                if (ret == 0)
+                        return ret;
+                dataoff += *matchoff;
+        }
+
+        if (in_header)
+                *in_header = 1;
+        return 1;
+}
+
+/* Locate a SIP header, parse the URI and return the offset and length of
+ * the address as well as the address and port themselves. A stream of
+ * headers can be parsed by handing in a non-NULL datalen and in_header
+ * pointer.
+ */
+int ct_sip_parse_header_uri(const struct nf_conn *ct, const char *dptr,
+                            unsigned int *dataoff, unsigned int datalen,
+                            enum sip_header_types type, int *in_header,
+                            unsigned int *matchoff, unsigned int *matchlen,
+                            union nf_inet_addr *addr, __be16 *port)
+{
+        const char *c, *limit = dptr + datalen;
+        unsigned int p;
+        int ret;
+
+        ret = ct_sip_walk_headers(ct, dptr, dataoff ? *dataoff : 0, datalen,
+                                  type, in_header, matchoff, matchlen);
+        WARN_ON(ret < 0);
+        if (ret == 0)
+                return ret;
+
+        if (!parse_addr(ct, dptr + *matchoff, &c, addr, limit))
+                return -1;
+        if (*c == ':') {
+                c++;
+                p = simple_strtoul(c, (char **)&c, 10);
+                if (p < 1024 || p > 65535)
+                        return -1;
+                *port = htons(p);
+        } else
+                *port = htons(SIP_PORT);
+
+        if (dataoff)
+                *dataoff = c - dptr;
+        return 1;
+}
+EXPORT_SYMBOL_GPL(ct_sip_parse_header_uri);
+
 /* SDP header parsing: a SDP session description contains an ordered set of
  * headers, starting with a section containing general session parameters,
  * optionally followed by multiple media descriptions.