提升C ++正则表达式以匹配SIP标头

Question

We have the following below to match a SIP Via header. We are using boost C++ regex

 Via: SIP/2.0/UDP 192.168.1.4:62486;rport;branch=z9hG4bK-524287-1---3ff9a622846c0a01;stck=3449406834;received=90.206.135.26 

Regex:

 std::regex g_Via;

 g_Via("(^Via:\\s+SIP/2\\.0/UDP\\s+)(((\\w|\\.|-)+):(\\d+))((;\\s*rport=(\\d+))|(;stck=(\\d+))|(;[^;\\n\\s]+)*)(\\s*$)",std::regex_constants::icase)

 std::match_results<std::string::const_iterator> result;
 bool valid = std::regex_match(line, result, g_Via);
 if(valid)
 {
    std::string rport = result[8].str();
    std::string stckval = result[9].str();
    // use these values
 }

What we would like is to grab the rport, received and stck parameters after the IP address. We can get the IP address using the above the expression but have a problem getting individual parameters.

The rport parameter can be either ;rport or ;rport=14838 ie on its own or with a value.

The problem we have is the params such as ;branch= ;received= can be in different positions

Answer 1

I wouldn't recommend "parsing" SIP headers using regex.

As mentioned in comments already, handling attributes becomes unwieldy. Also, you will find there are subtle details in the specification (rfc 2616/rfc 822) that make it hard to get right.

I've created a SIP header parser using Boost Spirit earlier:

• How to parse multi-line headers of SIP message using regex?

I've actually live-streamed creating that parser. Here's the vods of the live stream in case you like to see: part #1 , part #2 , part #3 and part #4 .

The benefits of using a parser generator here is that you don't end up with raw match groups, but can parse directly into something useful for futher processing, eg

using Headers = std::map<std::string, std::string>;

---

Live On Coliru

//#define BOOST_SPIRIT_DEBUG
#include <boost/fusion/adapted/std_pair.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/algorithm/string/trim.hpp>
#include <map>

using Headers = std::map<std::string, std::string>;

template <typename It> Headers parse_headers(It first, It last) 
{
    using namespace boost::spirit::qi;

    auto& crlf       = "\r\n";
    auto& tspecials = " \t><@,;:\\\"/][?=}{:";

    rule<It, std::string()> token, value;

    token = +~char_(tspecials); // FIXME? should filter CTLs
    value = *(char_ - (crlf >> &(~blank | eoi)));
    BOOST_SPIRIT_DEBUG_NODES((token)(value));

  //value = *(omit[ crlf >> !(~blank | eoi) ] >> attr(' ') | (char_ - crlf));

    Headers headers;
    bool ok = phrase_parse(first, last, (token >> ':' >> value) % crlf >> omit[*lit(crlf)], blank, headers);

#ifdef DEBUG
    if (ok)          std::cerr << "DEBUG: Parse success\n";
    else             std::cerr << "DEBUG: Parse failed\n";
    if (first!=last) std::cerr << "DEBUG: Remaining unparsed input: '" << std::string(first,last) << "'\n";
#endif

    if (ok && (first==last))
        return headers;

    throw std::runtime_error("Parse error in headers\n"); // TODO FIXME
}

int main()
{
    boost::spirit::istream_iterator iter(std::cin >> std::noskipws), end;

    for (auto& header : parse_headers(iter, end)) {
        std::cout << "Key: '" << header.first << "', Value: '" << header.second << "'\n";
    }
}

For input:

Via: SIP/2.0/UDP 10.10.1.99:5060;branch=z9hG4bK343bf628;rport
Contact: <sip:15@10.10.1.99>
Call-ID: 326371826c80e17e6cf6c29861eb2933@10.10.1.99
CSeq: 102 INVITE
User-Agent: Asterisk PBX
Max-Forwards: 70
Date: Wed, 06 Dec 2009 14:12:45 GMT
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Supported: replaces
Content-Type: application/sdp
Content-Length: 258
From: "Test 15" <sip:15@10.10.1.99>
 ; tag   =    fromtag
To: <sip:13@10.10.1.13>;tag=totag

It prints the output

Key: 'Allow', Value: 'INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY'
Key: 'CSeq', Value: '102 INVITE'
Key: 'Call-ID', Value: '326371826c80e17e6cf6c29861eb2933@10.10.1.99'
Key: 'Contact', Value: '<sip:15@10.10.1.99>'
Key: 'Content-Length', Value: '258'
Key: 'Content-Type', Value: 'application/sdp'
Key: 'Date', Value: 'Wed, 06 Dec 2009 14:12:45 GMT'
Key: 'From', Value: '"Test 15" <sip:15@10.10.1.99>
 ; tag   =    fromtag'
Key: 'Max-Forwards', Value: '70'
Key: 'Supported', Value: 'replaces'
Key: 'To', Value: '<sip:13@10.10.1.13>;tag=totag'
Key: 'User-Agent', Value: 'Asterisk PBX'
Key: 'Via', Value: 'SIP/2.0/UDP 10.10.1.99:5060;branch=z9hG4bK343bf628;rport'

Answer 2

Depending on what language you're working with, dealing with the attributes may be better done separately from the regex. You can use the regex to extract each attribute (or perhaps the entire attribute string--everything from the first ; to the end). After that, you can split the attribute string using ; as the delimiter. Both Python and PHP, for example, have easy functions to do this ( split() in Python, and explode() in PHP). You can then split each attribute by the = to separate the attribute name from the attribute value.

Answer 3

You're using too many groups I couldn't keep track, so I removed most of them. This will work in any of the languages you mentioned.

• (?<Named> groups) may not be supported in some flavors, but you can easily change it to a normal (group) . I used them for practicity.

Regex

^Via:\s+SIP\/2\.0\/UDP\s+                # header
([-.\w]+):(\d+)                          # IP (group 1) and port (group 2)
(?:                                      # ITERATE
    (?<received>;received=[.\d]+)        #   received (group "received")
  |                                      #
    (?<rport>;rport                      #   rport (group "rport")
        (?:=(?<rportval>[0-9]+))?        #    with optional num (group "rportval")
    )                                    #
  |                                      #
    (?<stck>;stck=\d+)                   #   stck (group "stck")
  |                                      #
    ;[^;\n\s=]+(?:=[^;]+)?               #   any other param (not captured)
)*                                       # Repeat iteration *
\s*$                                     # to EoL

One-liner:

^Via:\s+SIP\/2\.0\/UDP\s+([-.\w]+):(\d+)(?:(?<received>;received=[.\d]+)|(?<rport>;rport(?:=(?<rportval>[0-9]+))?)|(?<stck>;stck=\d+)|;[^;\n\s=]+(?:=[^;]+)?)*\s*$

---

Code

Using Boost.Regex :

#include <iostream>
#include <boost/regex.hpp>
using namespace std;
using namespace boost;


int main  () {
    string subject = "Via: SIP/2.0/UDP 192.168.1.4:62486;rport=12345;branch=z9hG4bK-524287-1---3ff9a622846c0a01;stck=3449406834;received=90.206.135.26";
    string pattern = "^Via:\\s+SIP/2\\.0/UDP\\s+([-.\\w]+):([0-9]+)(?:(?<received>;received=[.0-9]+)|(?<rport>;rport(?:=(?<rportval>[0-9]+))?)|(?<stck>;stck=[0-9]+)|;[^;\\n\\s=]+(?:=[^;]*)?)*\\s*$";
    smatch match;


    const regex re(pattern);
    if (regex_search(subject, match, re)) {
        string received = match["received"];
        string rport = match["rport"];
        string rportval = match["rportval"];
        string stck = match["stck"];
        cout << "rport = " << rport << endl << "rportval = " << rportval << endl;
    } else {
        cout << "NO MATCH" << endl;
    }
    return 0;
}

Output:

rport = ;rport=12345
rportval = 12345

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