Fix coverity detected issues in dnsmasq.c

Error: DEADCODE (CWE-561): [#def12]
dnsmasq-2.86rc3/src/dnsmasq.c:37: assignment: Assigning: "bind_fallback" = "0".
dnsmasq-2.86rc3/src/dnsmasq.c:927: const: At condition "bind_fallback", the value of "bind_fallback" must be equal to 0.
dnsmasq-2.86rc3/src/dnsmasq.c:927: dead_error_condition: The condition "bind_fallback" cannot be true.
dnsmasq-2.86rc3/src/dnsmasq.c:928: dead_error_line: Execution cannot reach this statement: "my_syslog(4, "setting --bin...".
dnsmasq-2.86rc3/src/dnsmasq.c:928: effectively_constant: Local variable "bind_fallback" is assigned only once, to a constant value, making it effectively constant throughout its scope. If this is not the intent, examine the logic to see if there is a missing assignment that would make "bind_fallback" not remain constant.
 #  926|
 #  927|     if (bind_fallback)
 #  928|->     my_syslog(LOG_WARNING, _("setting --bind-interfaces option because of OS limitations"));
 #  929|
 #  930|     if (option_bool(OPT_NOWILD))

Error: REVERSE_NEGATIVE (CWE-191): [#def13]
dnsmasq-2.86rc3/src/dnsmasq.c:383: negative_sink_in_call: Passing "dnsmasq_daemon->pxefd" to a parameter that cannot be negative.
dnsmasq-2.86rc3/src/dnsmasq.c:1086: check_after_sink: You might be using variable "dnsmasq_daemon->pxefd" before verifying that it is >= 0.
 # 1084|   	{
 # 1085|   	  poll_listen(daemon->dhcpfd, POLLIN);
 # 1086|-> 	  if (daemon->pxefd != -1)
 # 1087|   	    poll_listen(daemon->pxefd, POLLIN);
 # 1088|   	}

Error: CHECKED_RETURN (CWE-252): [#def18]
dnsmasq-2.86rc3/src/dnsmasq.c:1582: check_return: Calling "fcntl(dnsmasq_daemon->helperfd, 4, i & 0xfffffffffffff7ff)" without checking return value. This library function may fail and return an error code.
 # 1580|   	    /* block in writes until all done */
 # 1581|   	    if ((i = fcntl(daemon->helperfd, F_GETFL)) != -1)
 # 1582|-> 	      fcntl(daemon->helperfd, F_SETFL, i & ~O_NONBLOCK);
 # 1583|   	    do {
 # 1584|   	      helper_write();

Error: CHECKED_RETURN (CWE-252): [#def22]
dnsmasq-2.86rc3/src/dnsmasq.c:1991: check_return: Calling "fcntl(confd, 4, flags & 0xfffffffffffff7ff)" without checking return value. This library function may fail and return an error code.
 # 1989|   		 Reset that here. */
 # 1990|   	      if ((flags = fcntl(confd, F_GETFL, 0)) != -1)
 # 1991|-> 		fcntl(confd, F_SETFL, flags & ~O_NONBLOCK);
 # 1992|
 # 1993|   	      buff = tcp_request(confd, now, &tcp_addr, netmask, auth_dns);

Error: CHECKED_RETURN (CWE-252): [#def26]
dnsmasq-2.86rc3/src/dnssec.c:727: check_return: Calling "extract_name" without checking return value (as is done elsewhere 9 out of 10 times).
dnsmasq-2.86rc3/src/dnssec.c:459: example_checked: Example 1: "extract_name(header, plen, &p, keyname, 1, 0)" has its value checked in "extract_name(header, plen, &p, keyname, 1, 0)".
dnsmasq-2.86rc3/src/dnssec.c:269: example_checked: Example 2: "extract_name(header, plen, &state->ip, state->buff, 1, 0)" has its value checked in "extract_name(header, plen, &state->ip, state->buff, 1, 0)".
dnsmasq-2.86rc3/src/dnssec.c:569: example_checked: Example 3: "extract_name(header, plen, &p, keyname, 1, 0)" has its value checked in "extract_name(header, plen, &p, keyname, 1, 0)".
dnsmasq-2.86rc3/src/rfc1035.c:648: example_checked: Example 4: "extract_name(header, qlen, &p1, name, 1, 0)" has its value checked in "extract_name(header, qlen, &p1, name, 1, 0)".
dnsmasq-2.86rc3/src/rfc1035.c:787: example_checked: Example 5: "extract_name(header, qlen, &p1, name, 1, 0)" has its value checked in "extract_name(header, qlen, &p1, name, 1, 0)".
 #  725|         /* namebuff used for workspace above, restore to leave unchanged on exit */
 #  726|         p = (unsigned char*)(rrset[0]);
 #  727|->       extract_name(header, plen, &p, name, 1, 0);
 #  728|
 #  729|         if (key)

Error: CHECKED_RETURN (CWE-252): [#def27]
dnsmasq-2.86rc3/src/dnssec.c:1020: check_return: Calling "extract_name" without checking return value (as is done elsewhere 7 out of 8 times).
dnsmasq-2.86rc3/src/auth.c:140: example_checked: Example 1: "extract_name(header, qlen, &p, name, 1, 4)" has its value checked in "extract_name(header, qlen, &p, name, 1, 4)".
dnsmasq-2.86rc3/src/dnssec.c:771: example_checked: Example 2: "extract_name(header, plen, &p, name, 1, 4)" has its value checked in "extract_name(header, plen, &p, name, 1, 4)".
dnsmasq-2.86rc3/src/hash-questions.c:57: example_checked: Example 3: "extract_name(header, plen, &p, name, 1, 4)" has its value checked in "extract_name(header, plen, &p, name, 1, 4)".
dnsmasq-2.86rc3/src/rfc1035.c:1028: example_checked: Example 4: "extract_name(header, qlen, &p, name, 1, 4)" has its value checked in "extract_name(header, qlen, &p, name, 1, 4)".
dnsmasq-2.86rc3/src/rfc1035.c:1438: example_checked: Example 5: "extract_name(header, qlen, &p, name, 1, 4)" has its value checked in "extract_name(header, qlen, &p, name, 1, 4)".
 # 1018|
 # 1019|     p = (unsigned char *)(header+1);
 # 1020|->   extract_name(header, plen, &p, name, 1, 4);
 # 1021|     p += 4; /* qtype, qclass */
 # 1022|

1 files changed, 7 insertions, 4 deletions

diff --git a/src/dnsmasq.c b/src/dnsmasq.c
index 602daed..3e1bfe8 100644
--- a/src/dnsmasq.c
+++ b/src/dnsmasq.c
@@ -34,7 +34,6 @@ static void poll_resolv(int force, int do_reload, time_t now);
 
 int main (int argc, char **argv)
 {
-  int bind_fallback = 0;
   time_t now;
   struct sigaction sigact;
   struct iname *if_tmp;
@@ -59,6 +58,8 @@ int main (int argc, char **argv)
   int did_bind = 0;
   struct server *serv;
   char *netlink_warn;
+#else
+  int bind_fallback = 0;
 #endif 
 #if defined(HAVE_DHCP) || defined(HAVE_DHCP6)
   struct dhcp_context *context;
@@ -377,7 +378,7 @@ int main (int argc, char **argv)
 	      bindtodevice(bound_device, daemon->dhcpfd);
 	      did_bind = 1;
 	    }
-	  if (daemon->enable_pxe && bound_device)
+	  if (daemon->enable_pxe && bound_device && daemon->pxefd != -1)
 	    {
 	      bindtodevice(bound_device, daemon->pxefd);
 	      did_bind = 1;
@@ -920,8 +921,10 @@ int main (int argc, char **argv)
     my_syslog(LOG_WARNING, _("warning: failed to change owner of %s: %s"), 
 	      daemon->log_file, strerror(log_err));
   
+#ifndef HAVE_LINUX_NETWORK
   if (bind_fallback)
     my_syslog(LOG_WARNING, _("setting --bind-interfaces option because of OS limitations"));
+#endif
 
   if (option_bool(OPT_NOWILD))
     warn_bound_listeners();
@@ -1575,7 +1578,7 @@ static void async_event(int pipe, time_t now)
 	  {
 	    /* block in writes until all done */
 	    if ((i = fcntl(daemon->helperfd, F_GETFL)) != -1)
-	      fcntl(daemon->helperfd, F_SETFL, i & ~O_NONBLOCK); 
+	      while(retry_send(fcntl(daemon->helperfd, F_SETFL, i & ~O_NONBLOCK)));
 	    do {
 	      helper_write();
 	    } while (!helper_buf_empty() || do_script_run(now));
@@ -1984,7 +1987,7 @@ static void check_dns_listeners(time_t now)
 		 attribute from the listening socket. 
 		 Reset that here. */
 	      if ((flags = fcntl(confd, F_GETFL, 0)) != -1)
-		fcntl(confd, F_SETFL, flags & ~O_NONBLOCK);
+		while(retry_send(fcntl(confd, F_SETFL, flags & ~O_NONBLOCK)));
 	      
 	      buff = tcp_request(confd, now, &tcp_addr, netmask, auth_dns);