CODEWITHSUNDEEP
cpointers
Crizly
Crizly

Reputation: 1009

C Pointer Values Being Mixed

I'm working with a packet capture library and i've got it to print out packet IP addresses to the console using which is working fine:

printf("       From: %s\n", inet_ntoa(ip->ip_src));
printf("         To: %s\n", inet_ntoa(ip->ip_dst));

A few lines under that I call a method in a different .C file using this passing the IP addresses and port number:

addpacket(0, inet_ntoa(ip->ip_src), inet_ntoa(ip->ip_dst), ntohs(tcp->th_dport));

The method is: void addpacket(int table, char *srcIP, char *dstIP, int port) {...}

But inside the addpacket method I have this printing to the console:

printf("---------------------SRC:%s\n", srcIP);
printf("---------------------DST:%s\n", dstIP);
printf("---------------------PRT:%i\n", port);

And I get a result like this:

---------------------SRC:192.168.1.64
---------------------DST:192.168.1.64
---------------------PRT:60549

where the Source and Destination IP addresses are always the same. I can't find anywhere that i've mixed it up though. If I print this to the console in the original .C file the correct IP addresses appear but something seems to be getting mixed up during the method call. Any ideas?

Upvotes: 0

Views: 35

Answers (1)

nneonneo
nneonneo

Reputation: 179422

inet_ntoa may use a static buffer to store the result, meaning that the second invocation of inet_ntoa overwrites the result from the first invocation. Use inet_ntop instead, which allows you to supply your own buffers.

Upvotes: 5

Related Questions