Date: Wed, 21 Jul 1999 11:59:31 +0530 From: "Ratnakar Tiwari" <rhtiwari@cygsoft.com> To: <freebsd-bugs@FreeBSD.ORG> Subject: Uninitialized function pointer in Network Address Translation code Message-ID: <001101bed342$646fbfa0$3e01010a@ratnakar>
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[-- Attachment #1 --] Hi, I am trying to figure out how Network Address Translation works and I was going through the FreeBSD source code for it.This source code was downloaded from: ftp.FreeBSD.org/pub/FreeBSD/FreeBSD-stable/src/sys/netinet . In file ip_input.c on line 163 a pointer is declared as follows: ip_nat_t *ip_nat_ptr ; ip_nat_t is a function type defined in ip_fw.h as typedef int ip_nat_t __P((struct ip **, struct mbuf **, struct ifnet *, int)); __P is a macro defined in ip_compat.h The function pointer ip_nat_ptr is used on line 441 of ip_input.c as: if (ip_nat_ptr && !(*ip_nat_ptr)(&ip, &m, m->m_pkthdr.rcvif, IP_NAT_IN) However I was unable to determine where this pointer is being initialized. Could somebody please explain to me what exactly is going on in the code? Thanks. Ratnakar [-- Attachment #2 --] <!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <HTML> <HEAD> <META content=text/html;charset=iso-8859-1 http-equiv=Content-Type> <META content='"MSHTML 4.72.3110.7"' name=GENERATOR> </HEAD> <BODY bgColor=#d0d0c8> <DIV><FONT color=#000000 size=2>Hi,<BR> I am trying to figure out how Network Address Translation works and I<BR>was going through the FreeBSD source code for it.This source code was<BR>downloaded from:<BR> ftp.FreeBSD.org/pub/FreeBSD/FreeBSD-stable/src/sys/netinet .</FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2>In file ip_input.c on line 163 a pointer is declared as follows:<BR>ip_nat_t *ip_nat_ptr ;</FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2>ip_nat_t is a function type defined in ip_fw.h as</FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2>typedef int ip_nat_t __P((struct ip **, struct mbuf **, struct ifnet *,<BR>int)); <BR> __P is a macro defined in ip_compat.h</FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2>The function pointer ip_nat_ptr is used on line 441 of ip_input.c as:</FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2> if (ip_nat_ptr && !(*ip_nat_ptr)(&ip, &m, m->m_pkthdr.rcvif, IP_NAT_IN)<BR> <BR>However I was unable to determine where this pointer is being<BR>initialized. </FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2>Could somebody please explain to me what exactly is going on in the code?</FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2>Thanks.</FONT></DIV> <DIV><FONT color=#000000 size=2></FONT> </DIV> <DIV><FONT color=#000000 size=2>Ratnakar</FONT></DIV></BODY></HTML>
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