Re: [fpc-pascal] Test for valid ip address

[Koenraad Lelong]

Op 28-07-16 om 10:38 schreef Christo:


The in_addr IP address type is a packed record of byte, so if an IP
address part larger than 255 is encountered in a string it will be
truncated when copied to the byte record using StrToHostAddr.  This
probably means you have to use some other means of detecting an invalid
address, or add a check for (tmpAddress <> IPAddressStr) to cater for
your situation.


Thanks,

I used the check :
(tmpAddress <> IPAddressStr)
in stead of
(tmpAddress='0.0.0.0')

Koenraad

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Re: [fpc-pascal] Test for valid ip address

[Rainer Stratmann]

Am Donnerstag, 28. Juli 2016, 10:26:32 schrieb Jonas Maebe:
> On 28/07/16 10:14, Koenraad Lelong wrote:
> > I need a way to test if an string containing an ipv4-address is really
> > an ipv4-address.
> > I tried
> > tmpAddress:=HostAddrToStr(StrToHostAddr(IPAddressStr));
> > writeln(tmpAddress);
> > 
> >  if (tmpAddress='0.0.0.0') then
> >  
> >   begin
> >   
> >writeln('Error in IP-address');
> >IPAddressStr:=tmpAddress;
> >   
> >   end;
> > 
> > When I enter 192.168.185.297 (i.e. not a valid ipv4 address) in
> > IPAddressStr I get
> > 192.168.185.41
> > not the expected error-message.
> 
> You can add a multiple of 256 to any octet of an IPv4 address in most
> programs. Try it in your browser, it will probably also work.

In Firefox 45.2.0 on Linux it does not work.
It is confusing anyway.
 
> 
> Jonas
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Re: [fpc-pascal] Test for valid ip address

[Christo]

On Thu, 2016-07-28 at 10:14 +0200, Koenraad Lelong wrote:
> When I enter 192.168.185.297 (i.e. not a valid ipv4 address) in 
> IPAddressStr I get
> 192.168.185.41
> not the expected error-message.
> 
> According to the rtl-manual :
> 
> function StrToHostAddr(IP: AnsiString) : in_addr
> Description: StrToHostAddr converts the string representation in IP to a 
> host address and returns the host
> address.
> Errors: On error, the host address is filled with zeroes.
> 
> I would think that converting those zeroes to a host-address would yield 
> 0.0.0.0.
> 
> Am I missing something ?
> Is there a better way, without using some other network-library ?

The in_addr IP address type is a packed record of byte, so if an IP
address part larger than 255 is encountered in a string it will be
truncated when copied to the byte record using StrToHostAddr.  This
probably means you have to use some other means of detecting an invalid
address, or add a check for (tmpAddress <> IPAddressStr) to cater for
your situation.

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Re: [fpc-pascal] Test for valid ip address

[Mattias Gaertner]

On Thu, 28 Jul 2016 10:26:32 +0200
Jonas Maebe  wrote:

> On 28/07/16 10:14, Koenraad Lelong wrote:
> > I need a way to test if an string containing an ipv4-address is really
> > an ipv4-address.
> > I tried
> > tmpAddress:=HostAddrToStr(StrToHostAddr(IPAddressStr));
> > writeln(tmpAddress);
> >  if (tmpAddress='0.0.0.0') then
> >   begin
> >writeln('Error in IP-address');
> >IPAddressStr:=tmpAddress;
> >   end;
> > When I enter 192.168.185.297 (i.e. not a valid ipv4 address) in
> > IPAddressStr I get
> > 192.168.185.41
> > not the expected error-message.  
> 
> You can add a multiple of 256 to any octet of an IPv4 address in most 
> programs. Try it in your browser, it will probably also work.

What browser supports that?

Mattias
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Re: [fpc-pascal] Test for valid ip address

[Rainer Stratmann]

The IP-Adress is a dword, but you can change, that it fits for you.


function str_getval( str : shortstring ) : longint;
var cod : longint;
begin
 val( str , result , cod );
end;

function ip_from_string( ipstr : shortstring ; out error : boolean ) : dword;
var
 c : char;
 ipn , pointanz : longint;
 x : longint;
 pstr : shortstring;
 ip : dword;


 procedure add_ip;
 begin
  ipn := str_getval( pstr );
  if ( ipn > 255 ) or ( pstr = '' ) then error := true;
  ip := ip shl 8;
  ip := ip or ipn;
  pstr := '';
 end;

begin
 ip := 0;
 pstr := '';
 error := false;
 pointanz := 0;
 for x := 1 to length( ipstr ) do begin
  c := ipstr[ x ];
  case c of
   '0'..'9' : pstr := pstr + c;
   '.' : begin
inc( pointanz );
add_ip;
   end;
   else error := true;
  end;
 end;
 add_ip;
 if pointanz <> 3 then error := true;
 if error then result := 0
  else result := ip;
end;



Am Donnerstag, 28. Juli 2016, 10:14:10 schrieb Koenraad Lelong:
> Hi,
> 
> I need a way to test if an string containing an ipv4-address is really
> an ipv4-address.
> I tried
> tmpAddress:=HostAddrToStr(StrToHostAddr(IPAddressStr));
> writeln(tmpAddress);
>   if (tmpAddress='0.0.0.0') then
>begin
> writeln('Error in IP-address');
> IPAddressStr:=tmpAddress;
>end;
> When I enter 192.168.185.297 (i.e. not a valid ipv4 address) in
> IPAddressStr I get
> 192.168.185.41
> not the expected error-message.
> 
> According to the rtl-manual :
> 
> function StrToHostAddr(IP: AnsiString) : in_addr
> Description: StrToHostAddr converts the string representation in IP to a
> host address and returns the host
> address.
> Errors: On error, the host address is filled with zeroes.
> 
> I would think that converting those zeroes to a host-address would yield
> 0.0.0.0.
> 
> Am I missing something ?
> Is there a better way, without using some other network-library ?
> 
> Koenraad.
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Re: [fpc-pascal] Test for valid ip address

[Jonas Maebe]

On 28/07/16 10:14, Koenraad Lelong wrote:

I need a way to test if an string containing an ipv4-address is really
an ipv4-address.
I tried
tmpAddress:=HostAddrToStr(StrToHostAddr(IPAddressStr));
writeln(tmpAddress);
 if (tmpAddress='0.0.0.0') then
  begin
   writeln('Error in IP-address');
   IPAddressStr:=tmpAddress;
  end;
When I enter 192.168.185.297 (i.e. not a valid ipv4 address) in
IPAddressStr I get
192.168.185.41
not the expected error-message.


You can add a multiple of 256 to any octet of an IPv4 address in most 
programs. Try it in your browser, it will probably also work.



Jonas
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[fpc-pascal] Test for valid ip address

[Koenraad Lelong]

Hi,

I need a way to test if an string containing an ipv4-address is really 
an ipv4-address.

I tried
tmpAddress:=HostAddrToStr(StrToHostAddr(IPAddressStr));
writeln(tmpAddress);
 if (tmpAddress='0.0.0.0') then
  begin
   writeln('Error in IP-address');
   IPAddressStr:=tmpAddress;
  end;
When I enter 192.168.185.297 (i.e. not a valid ipv4 address) in 
IPAddressStr I get

192.168.185.41
not the expected error-message.

According to the rtl-manual :

function StrToHostAddr(IP: AnsiString) : in_addr
Description: StrToHostAddr converts the string representation in IP to a 
host address and returns the host

address.
Errors: On error, the host address is filled with zeroes.

I would think that converting those zeroes to a host-address would yield 
0.0.0.0.


Am I missing something ?
Is there a better way, without using some other network-library ?

Koenraad.
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