bb_full_fd_action: remove potential xmalloc from NOFORK path

cat: stop using stdio.h opens
libbb: introduce & use open[3]_or_warn
function                                             old     new   delta
open3_or_warn                                          -      54     +54
bb_cat                                               115     144     +29
open_or_warn                                           -      25     +25
unlzma                                              2404    2412      +8
chattr_main                                          334     339      +5
xstrtoul_range_sfx                                   251     255      +4
telnet_main                                         1514    1510      -4
static.opt                                             4       -      -4
qgravechar                                           122     118      -4
fuser_add_pid                                         61      54      -7
fuser_add_inode                                      154     147      -7
writeFileToTarball                                  1542    1534      -8
refresh                                             1156    1148      -8
do_show                                              856     846     -10
read_leases                                          212     200     -12
setup_redirects                                      236     222     -14
iproute_list_or_flush                               1582    1568     -14
read_config                                          427     411     -16
write_leases                                         284     264     -20
hash_file                                            338     318     -20
copy_file                                           1760    1740     -20
do_iproute                                          2610    2588     -22
bb_full_fd_action                                    320     269     -51
open_to_or_warn                                      103      49     -54
fuser_main                                          1660    1596     -64
.rodata                                           131160  131096     -64
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 4/19 up/down: 125/-423)        Total: -298 bytes

3 files changed, 5 insertions, 10 deletions

diff --git a/networking/libiproute/iproute.c b/networking/libiproute/iproute.c
index a19586c..23d4163 100644
--- a/networking/libiproute/iproute.c
+++ b/networking/libiproute/iproute.c
@@ -484,10 +484,9 @@ static int rtnl_rtcache_request(struct rtnl_handle *rth, int family)
 static void iproute_flush_cache(void)
 {
 	static const char fn[] = "/proc/sys/net/ipv4/route/flush";
-	int flush_fd = open(fn, O_WRONLY);
+	int flush_fd = open_or_warn(fn, O_WRONLY);
 
 	if (flush_fd < 0) {
-		bb_perror_msg("cannot open '%s'", fn);
 		return;
 	}
 
diff --git a/networking/libiproute/iptunnel.c b/networking/libiproute/iptunnel.c
index 52a5099..a2eb0cc 100644
--- a/networking/libiproute/iptunnel.c
+++ b/networking/libiproute/iptunnel.c
@@ -426,10 +426,9 @@ static void do_tunnels_list(struct ip_tunnel_parm *p)
 	int type;
 	struct ip_tunnel_parm p1;
 	char buf[512];
-	FILE *fp = fopen("/proc/net/dev", "r");
+	FILE *fp = fopen_or_warn("/proc/net/dev", "r");
 
 	if (fp == NULL) {
-		bb_perror_msg("fopen");
 		return;
 	}
 
diff --git a/networking/udhcp/files.c b/networking/udhcp/files.c
index ab6f4a3..41c8717 100644
--- a/networking/udhcp/files.c
+++ b/networking/udhcp/files.c
@@ -311,9 +311,8 @@ int read_config(const char *file)
 		if (keywords[i].def[0])
 			keywords[i].handler(keywords[i].def, keywords[i].var);
 
-	in = fopen(file, "r");
+	in = fopen_or_warn(file, "r");
 	if (!in) {
-		bb_error_msg("cannot open config file: %s", file);
 		return 0;
 	}
 
@@ -360,9 +359,8 @@ void write_leases(void)
 	time_t curr = time(0);
 	unsigned long tmp_time;
 
-	fp = open(server_config.lease_file, O_WRONLY|O_CREAT|O_TRUNC, 0666);
+	fp = open3_or_warn(server_config.lease_file, O_WRONLY|O_CREAT|O_TRUNC, 0666);
 	if (fp < 0) {
-		bb_error_msg("cannot open %s for writing", server_config.lease_file);
 		return;
 	}
 
@@ -401,9 +399,8 @@ void read_leases(const char *file)
 	unsigned int i = 0;
 	struct dhcpOfferedAddr lease;
 
-	fp = open(file, O_RDONLY);
+	fp = open_or_warn(file, O_RDONLY);
 	if (fp < 0) {
-		bb_error_msg("cannot open %s for reading", file);
 		return;
 	}