serdev.sgml

SIP Express Router, Linux下的SIP代理服务器,小巧实用,开发测试VoIP设备和应用的必备.

		<listitem>
		    <para>
			<structfield>uri</structfield> - Request <acronym>URI</acronym>.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>version</structfield> - Version string.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>method_value</structfield> - Parsed method. Field method which is of
			type <type>str</type> will be converted to integer and stored here. This is good for comparison,
			integer comparison is much faster then string comparison.
		    </para>
		</listitem>
	    </itemizedlist>

	    <para>
		<emphasis>Description of Response Related Fields:</emphasis>
	    </para>

	    <itemizedlist>
		<listitem>
		    <para>
			<structfield>version</structfield> - Version string.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>status</structfield> - Response status code as string.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>reason</structfield> - Response reason string as in the message.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>statuscode</structfield> - Response status code converted to integer.
		    </para>
		</listitem>
	    </itemizedlist>

	</section> <!-- msg-start -->

	<section id="sip-msg">
	    <title>Structure <structname>sip_msg</structname></title>
	    <para>
		This is the most important structure in the whole server. This structure represents
		a <acronym>SIP</acronym> message. When a message is received, it is immediately converted
		into this structure and all operations are performed over the structure. After the server
		finished processing, this structure is converted back to character array
		buffer and the buffer is sent out.
	    </para>
	    <para><emphasis>Structure Declaration:</emphasis></para>
	    <programlisting format="linespecific">
struct sip_msg {
    unsigned int id;               /* message id, unique/process*/
    struct msg_start first_line;   /* Message first line */
    struct via_body* via1;         /* The first via */
    struct via_body* via2;         /* The second via */
    struct hdr_field* headers;     /* All the parsed headers*/
    struct hdr_field* last_header; /* Pointer to the last parsed header*/
    int parsed_flag;               /* Already parsed header field types */

    /* Via, To, CSeq, Call-Id, From, end of header*/
    /* first occurrence of it; subsequent occurrences 
     * saved in 'headers' 
     */

    struct hdr_field* h_via1;
    struct hdr_field* h_via2;
    struct hdr_field* callid;
    struct hdr_field* to;
    struct hdr_field* cseq;
    struct hdr_field* from;
    struct hdr_field* contact;
    struct hdr_field* maxforwards;
    struct hdr_field* route;
    struct hdr_field* record_route;
    struct hdr_field* content_type;
    struct hdr_field* content_length;
    struct hdr_field* authorization;
    struct hdr_field* expires;
    struct hdr_field* proxy_auth;
    struct hdr_field* www_auth;
    struct hdr_field* supported;
    struct hdr_field* require;
    struct hdr_field* proxy_require;
    struct hdr_field* unsupported;
    struct hdr_field* allow;
    struct hdr_field* event;

    char* eoh;        /* pointer to the end of header (if found) or null */
    char* unparsed;   /* here we stopped parsing*/

    struct ip_addr src_ip;
    struct ip_addr dst_ip;
		
    char* orig;       /* original message copy */
    char* buf;        /* scratch pad, holds a modified message,
                       *  via, etc. point into it 
		       */
    unsigned int len; /* message len (orig) */

    /* modifications */
		
    str new_uri;               /* changed first line uri*/
    int parsed_uri_ok;         /* 1 if parsed_uri is valid, 0 if not */
    struct sip_uri parsed_uri; /* speed-up > keep here the parsed uri*/
		
    struct lump* add_rm;         /* used for all the forwarded 
                                  * requests */
    struct lump* repl_add_rm;    /* used for all the forwarded replies */
    struct lump_rpl *reply_lump; /* only for locally generated replies !!!*/

    char add_to_branch_s[MAX_BRANCH_PARAM_LEN];
    int add_to_branch_len;
		
    /* index to TM hash table; stored in core to avoid unnecessary calcs */
    unsigned int  hash_index;
		
    /* allows to set various flags on the message; may be used for 
     * simple inter-module communication or remembering processing state
     * reached 
     */
    flag_t flags;	
};
</programlisting>
	    <para>
		<emphasis>Field Description:</emphasis>
	    </para>
	    <itemizedlist>
		<listitem>
		    <para>
			<structfield>id</structfield> - Unique ID of the message within a process context.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>first_line</structfield> - Parsed first line of the message.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>via1</structfield> - The first Via - parsed.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>via2</structfield> - The second Via - parsed.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>headers</structfield> - Linked list of all parsed headers.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>last_header</structfield> - Pointer to the last parsed header (parsing is incremental,
			that means that the parser will stop if all requested headers were found and next time it will
			continue at the place where it stopped previously. Therefore this field will not point to the
			last header of the message if the whole message hasn't been parsed yet).
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>parsed_flag</structfield> - Already parsed header field types (bitwise OR).
		    </para>
		</listitem>
	    </itemizedlist>

	    <para>
		The following fields are set to zero if the corresponding header field was not found in the
		message or hasn't been parsed yet. (These fields are called hooks - they always point to the first
		occurrence if there is more than one header field of the same type).
	    </para>
	    <itemizedlist>
		<listitem>
		    <para>
			<structfield>h_via1</structfield> - Pointer to the first Via header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>h_via2</structfield> - Pointer to the second Via header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>callid</structfield> - Pointer to the first Call-ID header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>to</structfield> - Pointer to the first To header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>cseq</structfield> - Pointer to the first CSeq header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>from</structfield> - Pointer to the first From header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>contact</structfield> - Pointer to the first Contact header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>maxforwards</structfield> - Pointer to the first Max-Forwards header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>route</structfield> - Pointer to the first Route header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>record_route</structfield> - Pointer to the first Record-Route header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>content_type</structfield> - Pointer to the first Content-Type header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>content_length</structfield> - Pointer to the first Content-Length header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>authorization</structfield> - Pointer to the first Authorization header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>expires</structfield> - Pointer to the first Expires header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>proxy_auth</structfield> - Pointer to the first Proxy-Authorize header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>www_auth</structfield> - Pointer to the first WWW-Authorize header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>supported</structfield> - Pointer to the first Supported header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>require</structfield> - Pointer to the first Require header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>proxy_require</structfield> - Pointer to the first Proxy-Require header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>unsupported</structfield> - Pointer to the first Unsupported header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>allow</structfield> - Pointer to the first Allow header field.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>event</structfield> - Pointer to the first Event header field.
		    </para>
		</listitem>
	    </itemizedlist>

	    <para>
		The following fields are mostly used internally by the server and should be modified through dedicated
		functions only.
	    </para>

	    <itemizedlist>
		<listitem>
		    <para>
			<structfield>eoh</structfield> - Pointer to the End of Header or null if not found yet (the field
			will be set if and only if the whole message was parsed already).
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>unparsed</structfield> - Pointer to the first unparsed character in the message.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>src_ip</structfield> - Sender's <acronym>IP</acronym> address.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>dst_ip</structfield> - Destination's <acronym>IP</acronym> address.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>orig</structfield> - Original (unmodified) message copy, this field will hold
			unmodified copy of the message during the whole message lifetime.
		    </para>
		</listitem>
		<listitem>
		    <para>
			<structfield>buf</structfield> - Message scratch-pad (modified copy of the message) - All modifications
			made to the message will be done here.
		    </para>
		</listitem>
		<listitem>
		    <para>