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util: Fix gethostname() and freeaddrinfo() calls 

I was passing the wrong size to the 'gethostname()' call because the
'hostname' is now dynamically allocated and cannot use 'sizeof' to get
its size.  This mistake causes that the obtained hostname is empty.

The 'freeaddrinfo()' was placed at the wrong place.  Fix it.

Fallback to '_POSIX_HOST_NAME_MAX' if 'sysconf()' fails.

Always null-terminate the 'hostname'.
This commit is contained in:
Aaron LI 2018-10-06 01:34:04 +08:00
parent 4dee666dcf
commit 4e69002432
1 changed files with 13 additions and 10 deletions
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23
src/util.c
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@ -6,7 +6,6 @@
#include <string.h> #include <string.h>
#include <unistd.h> #include <unistd.h>
// hostname
#include <limits.h> #include <limits.h>
#include <stdio.h> #include <stdio.h>
#include <sys/types.h> #include <sys/types.h>
@ -24,23 +23,27 @@ void hostname(char** out)
struct addrinfo hints; struct addrinfo hints;
struct addrinfo* info; struct addrinfo* info;
char* hostname; char* hostname;
char* dot;
int host_name_max;
int result; int result;
if ((host_name_max = sysconf(_SC_HOST_NAME_MAX)) == -1) int maxlen = sysconf(_SC_HOST_NAME_MAX);
if (maxlen < 0)
{ {
perror("sysconf(_SC_HOST_NAME_MAX)"); maxlen = _POSIX_HOST_NAME_MAX;
exit(1);
} }
if ((hostname = malloc(host_name_max+1)) == NULL) if ((hostname = malloc(maxlen + 1)) == NULL)
{ {
perror("malloc"); perror("malloc");
exit(1); exit(1);
} }
gethostname(hostname, sizeof(hostname)); if (gethostname(hostname, maxlen) < 0)
{
perror("gethostname");
exit(1);
}
hostname[maxlen] = '\0';
memset(&hints, 0, sizeof hints); memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM; hints.ai_socktype = SOCK_STREAM;
@ -49,8 +52,9 @@ void hostname(char** out)
if ((result == 0) && (info != NULL)) if ((result == 0) && (info != NULL))
{ {
dot = strchr(info->ai_canonname, '.'); char* dot = strchr(info->ai_canonname, '.');
*out = strndup(info->ai_canonname, dot - info->ai_canonname); *out = strndup(info->ai_canonname, dot - info->ai_canonname);
freeaddrinfo(info);
} }
else else
{ {
@ -58,7 +62,6 @@ void hostname(char** out)
} }
hostname_backup = *out; hostname_backup = *out;
freeaddrinfo(info);
free(hostname); free(hostname);
} }