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authorRich Felker <dalias@aerifal.cx>2011-09-21 23:17:45 -0400
committerRich Felker <dalias@aerifal.cx>2011-09-21 23:17:45 -0400
commitbf027ca5e0c7bc0b90e84dcbb1d7cbea6ed1e3ef (patch)
tree09873e1c784b4ac272accec695153bb7f6a2eb6b /src/network
parent81a5577a860b1d320239a84c84266e4d7045f450 (diff)
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use poll rather than select in dns lookups (also clock_gettime)
if the file descriptor resource limit has been increased past FD_SETSIZE, this is actually a security issue; we could write past the end of the fd_set object. using poll makes it a non-issue, and simplifies the code at the same time. also, use clock_gettime instead of gettimeofday, for reduced bloat and better entropy.
Diffstat (limited to 'src/network')
-rw-r--r--src/network/__dns.c22
1 files changed, 10 insertions, 12 deletions
diff --git a/src/network/__dns.c b/src/network/__dns.c
index b3c876f3..a5458b51 100644
--- a/src/network/__dns.c
+++ b/src/network/__dns.c
@@ -5,8 +5,7 @@
#include <limits.h>
#include <string.h>
#include <sys/socket.h>
-#include <sys/select.h>
-#include <sys/time.h>
+#include <poll.h>
#include <netinet/in.h>
#include <time.h>
#include <ctype.h>
@@ -16,7 +15,7 @@
#include "stdio_impl.h"
#define TIMEOUT 5
-#define RETRY 1
+#define RETRY 1000
#define PACKET_MAX 512
#define PTR_MAX (64 + sizeof ".in-addr.arpa")
@@ -40,8 +39,8 @@ int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
int got = 0, failed = 0;
int errcode = EAI_AGAIN;
int i, j;
- struct timeval tv;
- fd_set fds;
+ struct timespec ts;
+ struct pollfd pfd;
int id;
int cs;
@@ -58,8 +57,8 @@ int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
ql = i+4;
/* Make a reasonably unpredictable id */
- gettimeofday(&tv, 0);
- id = tv.tv_usec + tv.tv_usec/256 & 0xffff;
+ clock_gettime(CLOCK_REALTIME, &ts);
+ id = ts.tv_nsec + ts.tv_nsec/65536UL & 0xffff;
/* Get nameservers from resolv.conf, fallback to localhost */
f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf);
@@ -94,6 +93,9 @@ int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
/* Nonblocking to work around Linux UDP select bug */
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);
+ pfd.fd = fd;
+ pfd.events = POLLIN;
+
/* Loop until we timeout; break early on success */
for (; time(0)-t0 < TIMEOUT; ) {
@@ -106,11 +108,7 @@ int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt)
}
/* Wait for a response, or until time to retry */
- FD_ZERO(&fds);
- FD_SET(fd, &fds);
- tv.tv_sec = RETRY;
- tv.tv_usec = 0;
- if (select(fd+1, &fds, 0, 0, &tv) <= 0) continue;
+ if (poll(&pfd, 1, RETRY) <= 0) continue;
/* Process any and all replies */
while (got+failed < rrcnt && (rlen = recvfrom(fd, r, 512, 0,