code for validating IPv4 address

**Burne C** · Nov 13 '05, 04:36 PM

Re: code for validating IPv4 address

"qazmlp" <qazmlp1209@red iffmail.com> wrote in message
news:db9bbf31.0 307270251.607a4 18c@posting.goo gle.com...[color=blue]
> What is the best & fastest way of validating an IPv4 address?
> Basically, the input can be either in IPAddressv4 or IPAddressv4:por t
> format.
>
> Currently I have the following code to validate the first format. Does
> anybody have any comment on this? Also, please suggest a mechanism to
> validate the second format(address: port) also.
>
> Thanks!
>
> -----------------------------
> #define INVALID -1
> #define VALID 0
>
> int validateIP(char *ipadd)
> {
> unsigned b1, b2, b3, b4;[/color]

I didn't see this kind of declaration before, you just used "unsigned" in here and no type
specifier. However, I compiled your code with no error in my. Is it legal for using "unsigned" alone
?
[color=blue]
> unsigned char c;
>
> if (sscanf(ipadd, "%3u.%3u.%3u.%3 u%c", &b1, &b2, &b3, &b4, &c) != 4)
> return INVALID;
>
> if ((b1 | b2 | b3 | b4) > 255) return INVALID;
> if (strspn(ipadd, "0123456789 .") < strlen(ipadd)) return INVALID;
> return VALID;
> }[/color]

--
BC

MG · Nov 13 '05, 04:36 PM

Re: code for validating IPv4 address

"qazmlp" <qazmlp1209@red iffmail.com> wrote in message
news:db9bbf31.0 307270251.607a4 18c@posting.goo gle.com...[color=blue]
> What is the best & fastest way of validating an IPv4 address?
> Basically, the input can be either in IPAddressv4 or IPAddressv4:por t
> format.
>
> Currently I have the following code to validate the first format. Does
> anybody have any comment on this? Also, please suggest a mechanism to
> validate the second format(address: port) also.
>
> Thanks!
>
> -----------------------------
> #define INVALID -1
> #define VALID 0
>
> int validateIP(char *ipadd)
> {
> unsigned b1, b2, b3, b4;
> unsigned char c;
>
> if (sscanf(ipadd, "%3u.%3u.%3u.%3 u%c", &b1, &b2, &b3, &b4, &c) != 4)
> return INVALID;
>
> if ((b1 | b2 | b3 | b4) > 255) return INVALID;
> if (strspn(ipadd, "0123456789 .") < strlen(ipadd)) return INVALID;
> return VALID;
> }[/color]

just an add on..
depending upon the situation, you might require some add on checks of the
reserved IP address...

MG

**Rouben Rostamian** · Nov 13 '05, 04:36 PM

Re: code for validating IPv4 address

In article <db9bbf31.03072 70251.607a418c@ posting.google. com>,
qazmlp <qazmlp1209@red iffmail.com> wrote:[color=blue]
>What is the best & fastest way of validating an IPv4 address?
>Basically, the input can be either in IPAddressv4 or IPAddressv4:por t
>format.
>
>Currently I have the following code to validate the first format. Does
>anybody have any comment on this? Also, please suggest a mechanism to
>validate the second format(address: port) also.[/color]

[code snipped]
[color=blue]
> if ((b1 | b2 | b3 | b4) > 255) return INVALID;[/color]

That's not good. Surely you meant:

if (b1 > 255 || b2 > 255 || b3 > 255 || b4 > 255 ) return INVALID;

--
Rouben Rostamian <rostamian@umbc .edu>

**Emmanuel Delahaye** · Nov 13 '05, 04:36 PM

Re: code for validating IPv4 address

In 'comp.lang.c', "Burne C" <nobody@notexis t.com> wrote:
[color=blue][color=green]
>> unsigned b1, b2, b3, b4;[/color]
>
> I didn't see this kind of declaration before, you just used "unsigned"
> in here and no type specifier. However, I compiled your code with no
> error in my. Is it legal for using "unsigned" alone ?[/color]

Yes, 'unsigned' a short name for 'unsigned int', like 'long' is a shortname
for 'long int' etc.

--
-ed- emdelYOURBRA@no os.fr [remove YOURBRA before answering me]
The C-language FAQ: http://www.eskimo.com/~scs/C-faq/top.html
<blank line>
FAQ de f.c.l.c : http://www.isty-info.uvsq.fr/~rumeau/fclc/

**Cael** · Nov 13 '05, 04:37 PM

Re: code for validating IPv4 address

"Rouben Rostamian" <rouben@pc18.ma th.umbc.edu> wrote in message
news:bg0ug1$621 $1@pc18.math.um bc.edu...[color=blue]
> In article <db9bbf31.03072 70251.607a418c@ posting.google. com>,
> qazmlp <qazmlp1209@red iffmail.com> wrote:[color=green]
> >What is the best & fastest way of validating an IPv4 address?
> >Basically, the input can be either in IPAddressv4 or IPAddressv4:por t
> >format.
> >
> >Currently I have the following code to validate the first format. Does
> >anybody have any comment on this? Also, please suggest a mechanism to
> >validate the second format(address: port) also.[/color]
>
> [code snipped]
>[color=green]
> > if ((b1 | b2 | b3 | b4) > 255) return INVALID;[/color]
>
>
> That's not good. Surely you meant:
>
> if (b1 > 255 || b2 > 255 || b3 > 255 || b4 > 255 ) return INVALID;
>[/color]

I think the statement (b1 | b2 | b3 | b4) > 255 is very effective, the
result of bitwise OR (b1 | b2 | b3 | b4) is bigger than 255 if any of them
is bigger than 255.

[color=blue]
>
> --
> Rouben Rostamian <rostamian@umbc .edu>[/color]

--
Cael

**qazmlp** · Nov 13 '05, 04:37 PM

Re: code for validating IPv4 address

qazmlp1209@redi ffmail.com (qazmlp) wrote in message news:<db9bbf31. 0307270251.607a 418c@posting.go ogle.com>...[color=blue]
> What is the best & fastest way of validating an IPv4 address?
> Basically, the input can be either in IPAddressv4 or IPAddressv4:por t
> format.
>
> Currently I have the following code to validate the first format. Does
> anybody have any comment on this? Also, please suggest a mechanism to
> validate the second format(address: port) also.
>
> Thanks!
>
> -----------------------------
> #define INVALID -1
> #define VALID 0
>
> int validateIP(char *ipadd)
> {
> unsigned b1, b2, b3, b4;
> unsigned char c;
>
> if (sscanf(ipadd, "%3u.%3u.%3u.%3 u%c", &b1, &b2, &b3, &b4, &c) != 4)
> return INVALID;
>
> if ((b1 | b2 | b3 | b4) > 255) return INVALID;
> if (strspn(ipadd, "0123456789 .") < strlen(ipadd)) return INVALID;
> return VALID;
> }[/color]

I am expecting your suggestions for validating the 'address:port' format.

Thanks!

**Dan Pop** · Nov 13 '05, 04:37 PM

Re: code for validating IPv4 address

In <db9bbf31.03072 70251.607a418c@ posting.google. com> qazmlp1209@redi ffmail.com (qazmlp) writes:
[color=blue]
>What is the best & fastest way of validating an IPv4 address?
>Basically, the input can be either in IPAddressv4 or IPAddressv4:por t
>format.
>
>Currently I have the following code to validate the first format. Does
>anybody have any comment on this? Also, please suggest a mechanism to
>validate the second format(address: port) also.
>
>#define INVALID -1
>#define VALID 0
>
>int validateIP(char *ipadd)
>{
> unsigned b1, b2, b3, b4;
> unsigned char c;
>
> if (sscanf(ipadd, "%3u.%3u.%3u.%3 u%c", &b1, &b2, &b3, &b4, &c) != 4)
> return INVALID;
>
> if ((b1 | b2 | b3 | b4) > 255) return INVALID;
> if (strspn(ipadd, "0123456789 .") < strlen(ipadd)) return INVALID;
> return VALID;
>}[/color]

This looks exactly like code I've posted a couple of years ago. The more
paranoid check at the end was added in response to some criticism from
Tak-Shing :-)

Extending it for IPAddressv4:por t shouldn't be that difficult to anyone
who has understood how the current version works (which, of course,
excludes qazmlp).

#define PORTMAX 65535 /* or whatever appropriate */

int validateIP(char *ipadd)
{
unsigned b1, b2, b3, b4, port = 0;
unsigned char c;
int rc;

rc = sscanf(ipadd, "%3u.%3u.%3u.%3 u:%u%c",
&b1, &b2, &b3, &b4, &port, &c);
if (rc != 4 && rc != 5) return INVALID;
if ((b1 | b2 | b3 | b4) > 255 || port > PORTMAX) return INVALID;
if (strspn(ipadd, "0123456789 .:") < strlen(ipadd)) return INVALID;
return VALID;
}

Trivia quiz: what is the purpose of the last check?

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Dan Pop** · Nov 13 '05, 04:37 PM

Re: code for validating IPv4 address

In <bg0l2f$7ev1@im sp212.netvigato r.com> "Burne C" <nobody@notexis t.com> writes:

[color=blue]
>I didn't see this kind of declaration before, you just used "unsigned" in here and no type
>specifier. However, I compiled your code with no error in my. Is it legal for using "unsigned" alone
>?[/color]

Here's the complete list of C99 type "aliases":

- short, signed short, short int, or signed short int
- unsigned short, or unsigned short int
- int, signed, or signed int
- unsigned, or unsigned int
- long, signed long, long int, or signed long int
- unsigned long, or unsigned long int
- long long, signed long long, long long int, or signed long long int
- unsigned long long, or unsigned long long int

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Dan Pop** · Nov 13 '05, 04:38 PM

Re: code for validating IPv4 address

In <3f253311.11430 993@news21.on.a ibn.com> Lew.Pitcher@td. com (Lew Pitcher) writes:
[color=blue]
>On 28 Jul 2003 13:49:08 GMT, Dan.Pop@cern.ch (Dan Pop) wrote:
>[snip][color=green]
>>
>> #define PORTMAX 65535 /* or whatever appropriate */
>>
>> int validateIP(char *ipadd)
>> {
>> unsigned b1, b2, b3, b4, port = 0;
>> unsigned char sep, c;
>> int rc;
>>
>> rc = sscanf(ipadd, "%3u.%3u.%3u.%3 u:%u%c",
>> &b1, &b2, &b3, &b4, &port, &c);
>> if (rc != 4 && rc != 5) return INVALID;
>> if ((b1 | b2 | b3 | b4) > 255 || port > PORTMAX) return INVALID;
>> if (strspn(ipadd, "0123456789 .:") < strlen(ipadd)) return INVALID;
>> return VALID;
>> }
>>
>>Trivia quiz: what is the purpose of the last check?[/color]
>
>Well, I won't profess to know the purpose of the last check, but it /will/
>reject an IP address string of "1.2.3.4=", where the prior tests would not.[/color]

The original version, as posted by the OP, would catch "1.2.3.4=" because
scanf would return 5 instead of 4. Yet, the test is still there.

This points out a bug in my version above: "1.2.3.4.5" will not be
identified as an invalid IP address. So, back to the drawing board:

rc = sscanf(ipadd, "%3u.%3u.%3u.%3 u%c%u%c",
&b1, &b2, &b3, &b4, &sep, &port, &c);
if (rc != 4 && rc != 6) return INVALID;
if (rc == 6 && sep != ':') return INVALID;
if ((b1 | b2 | b3 | b4) > 255 || port > PORTMAX) return INVALID;
if (strspn(ipadd, "0123456789 .:") < strlen(ipadd)) return INVALID;
return VALID;

Why is the last check still there?

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**James Antill** · Nov 13 '05, 04:38 PM

Re: code for validating IPv4 address

On Mon, 28 Jul 2003 18:13:41 +0000, Dan Pop wrote:
[color=blue]
> The original version, as posted by the OP, would catch "1.2.3.4=" because
> scanf would return 5 instead of 4. Yet, the test is still there.
>
> This points out a bug in my version above: "1.2.3.4.5" will not be
> identified as an invalid IP address. So, back to the drawing board:
>
> rc = sscanf(ipadd, "%3u.%3u.%3u.%3 u%c%u%c",
> &b1, &b2, &b3, &b4, &sep, &port, &c);
> if (rc != 4 && rc != 6) return INVALID;
> if (rc == 6 && sep != ':') return INVALID;
> if ((b1 | b2 | b3 | b4) > 255 || port > PORTMAX) return INVALID;
> if (strspn(ipadd, "0123456789 .:") < strlen(ipadd)) return INVALID;
> return VALID;
>
> Why is the last check still there?[/color]

I'll assume because strtoul() doens't do any checking on input, which
makes "-0" valid as an unsidnged number.

You could also argue that because of locale's the above will catch...

0.0.0.0:1,000

....but it won't if the thousands seperator is '.' (which it is in germany
for instance) ... so it doesn't catch that.

The truley strict versions I've seen/written don't use scanf().

--
James Antill -- james@and.org
Need an efficent and powerful string library for C?

Vstr documentation -- overview

http://www.and.org/vstr/

**qazmlp** · Nov 13 '05, 04:38 PM

Re: code for validating IPv4 address

Dan.Pop@cern.ch (Dan Pop) wrote in message news:<bg39kk$ru 0$2@sunnews.cer n.ch>...[color=blue]
> In <db9bbf31.03072 70251.607a418c@ posting.google. com> qazmlp1209@redi ffmail.com (qazmlp) writes:
>[color=green]
> >What is the best & fastest way of validating an IPv4 address?
> >Basically, the input can be either in IPAddressv4 or IPAddressv4:por t
> >format.
> >
> >Currently I have the following code to validate the first format. Does
> >anybody have any comment on this? Also, please suggest a mechanism to
> >validate the second format(address: port) also.
> >
> >#define INVALID -1
> >#define VALID 0
> >
> >int validateIP(char *ipadd)
> >{
> > unsigned b1, b2, b3, b4;
> > unsigned char c;
> >
> > if (sscanf(ipadd, "%3u.%3u.%3u.%3 u%c", &b1, &b2, &b3, &b4, &c) != 4)
> > return INVALID;
> >
> > if ((b1 | b2 | b3 | b4) > 255) return INVALID;
> > if (strspn(ipadd, "0123456789 .") < strlen(ipadd)) return INVALID;
> > return VALID;
> >}[/color]
>
> This looks exactly like code I've posted a couple of years ago. The more
> paranoid check at the end was added in response to some criticism from
> Tak-Shing :-)
>
> Extending it for IPAddressv4:por t shouldn't be that difficult to anyone
> who has understood how the current version works (which, of course,
> excludes qazmlp).
>
> #define PORTMAX 65535 /* or whatever appropriate */
>
> int validateIP(char *ipadd)
> {
> unsigned b1, b2, b3, b4, port = 0;
> unsigned char c;
> int rc;
>
> rc = sscanf(ipadd, "%3u.%3u.%3u.%3 u:%u%c",
> &b1, &b2, &b3, &b4, &port, &c);
> if (rc != 4 && rc != 5) return INVALID;
> if ((b1 | b2 | b3 | b4) > 255 || port > PORTMAX) return INVALID;
> if (strspn(ipadd, "0123456789 .:") < strlen(ipadd)) return INVALID;
> return VALID;
> }[/color]
As I mentioned in my original post, the same function should handle
the input which can either be in 'ipaddress' or 'ipaddress:port '. Is
this possible with a single sscanf? Or, should I do like this:
call strchr() to find ':'
If found, call the 2-nd version of validateIP() which handles
ipaddress:port' format.
else, call the 1st version of validateIP() which handles 'ipaddress'
format.
[color=blue]
>
> Trivia quiz: what is the purpose of the last check?
>
> Dan[/color]

**Dan Pop** · Nov 13 '05, 04:39 PM

Re: code for validating IPv4 address

In <db9bbf31.03072 82025.24b20445@ posting.google. com> qazmlp1209@redi ffmail.com (qazmlp) writes:
[color=blue]
>Dan.Pop@cern.c h (Dan Pop) wrote in message news:<bg39kk$ru 0$2@sunnews.cer n.ch>...[color=green]
>>
>> Extending it for IPAddressv4:por t shouldn't be that difficult to anyone
>> who has understood how the current version works (which, of course,
>> excludes qazmlp).
>>
>> #define PORTMAX 65535 /* or whatever appropriate */
>>
>> int validateIP(char *ipadd)
>> {
>> unsigned b1, b2, b3, b4, port = 0;
>> unsigned char c;
>> int rc;
>>
>> rc = sscanf(ipadd, "%3u.%3u.%3u.%3 u:%u%c",
>> &b1, &b2, &b3, &b4, &port, &c);
>> if (rc != 4 && rc != 5) return INVALID;
>> if ((b1 | b2 | b3 | b4) > 255 || port > PORTMAX) return INVALID;
>> if (strspn(ipadd, "0123456789 .:") < strlen(ipadd)) return INVALID;
>> return VALID;
>> }[/color]
>As I mentioned in my original post, the same function should handle
>the input which can either be in 'ipaddress' or 'ipaddress:port '. Is
>this possible with a single sscanf?[/color]

If you were not the idiot you actually are, you'd have noticed that this
is exactly what the code I've posted is supposed to do.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Dan Pop** · Nov 13 '05, 04:39 PM

Re: code for validating IPv4 address

In <pan.2003.07.28 .21.10.23.93056 6@and.org> "James Antill" <james-netnews@and.org > writes:
[color=blue]
>On Mon, 28 Jul 2003 18:13:41 +0000, Dan Pop wrote:
>[color=green]
>> The original version, as posted by the OP, would catch "1.2.3.4=" because
>> scanf would return 5 instead of 4. Yet, the test is still there.
>>
>> This points out a bug in my version above: "1.2.3.4.5" will not be
>> identified as an invalid IP address. So, back to the drawing board:
>>
>> rc = sscanf(ipadd, "%3u.%3u.%3u.%3 u%c%u%c",
>> &b1, &b2, &b3, &b4, &sep, &port, &c);
>> if (rc != 4 && rc != 6) return INVALID;
>> if (rc == 6 && sep != ':') return INVALID;
>> if ((b1 | b2 | b3 | b4) > 255 || port > PORTMAX) return INVALID;
>> if (strspn(ipadd, "0123456789 .:") < strlen(ipadd)) return INVALID;
>> return VALID;
>>
>> Why is the last check still there?[/color]
>
> I'll assume because strtoul() doens't do any checking on input, which
>makes "-0" valid as an unsidnged number.[/color]

Even simpler, +12 is a valid unsigned number. The other issue is embedded
white space: "+12. 34. 56. 78" would pass all the other tests, yet it
hardly looks like a valid IP address.
[color=blue]
> You could also argue that because of locale's the above will catch...[/color]

The code was meant to be used in the C locale...

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de

**Default User** · Nov 13 '05, 04:40 PM

Re: code for validating IPv4 address

Dan Pop wrote:
[color=blue]
> If you were not the idiot you actually are, you'd have noticed that this
> is exactly what the code I've posted is supposed to do.[/color]

I still can't figure out if this guy (quasilump or whatever) is an
elaborate troll or the world's slowest-learning programmer. At least in
this thread he actually interacted a bit with the respondents. Usually
he declines to respond to any comments or questions.

Brian Rodenborn

code for validating IPv4 address

code for validating IPv4 address

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