From 693c9256e416fb320622aeaf3ac2f7a854d556f1 Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Sat, 13 Nov 2010 08:37:33 -0500
Subject: [PATCH] Add safe_read() to ncmlib and use it in ndhc.

---
 ncmlib/io.c         | 26 +++++++++++++++++++----
 ncmlib/io.h         |  3 ++-
 ndhc/clientpacket.c | 52 +++++++++++++++++++++------------------------
 ndhc/packet.c       |  6 +++---
 4 files changed, 51 insertions(+), 36 deletions(-)

diff --git a/ncmlib/io.c b/ncmlib/io.c
index 97cf8a7..3bda0dc 100644
--- a/ncmlib/io.c
+++ b/ncmlib/io.c
@@ -1,5 +1,5 @@
 /* io.c - light wrappers for POSIX i/o functions
- * Time-stamp: <2010-11-13 08:08:39 njk>
+ * Time-stamp: <2010-11-13 08:22:53 njk>
  *
  * (c) 2010 Nicholas J. Kain <njkain at gmail dot com>
  * All rights reserved.
@@ -30,11 +30,29 @@
 #include <unistd.h>
 #include <errno.h>
 
-// returns -1 on error, >= 0 on success
+/* returns -1 on error, >= 0 and equal to # chars read on success */
+int safe_read(int fd, char *buf, int len)
+{
+    int r, s = 0;
+    while (s < len) {
+        r = read(fd, buf + s, len - s);
+        if (r == 0)
+            break;
+        if (r == -1) {
+            if (errno == EINTR)
+                continue;
+            else
+                return -1;
+        }
+        s += r;
+    }
+    return s;
+}
+
+/* returns -1 on error, >= 0 and equal to # chars written on success */
 int safe_write(int fd, const char *buf, int len)
 {
-    int r;
-    int s = 0;
+    int r, s = 0;
     while (s < len) {
         r = write(fd, buf + s, len - s);
         if (r == -1) {
diff --git a/ncmlib/io.h b/ncmlib/io.h
index 719dce9..9e24419 100644
--- a/ncmlib/io.h
+++ b/ncmlib/io.h
@@ -1,5 +1,5 @@
 /* io.h - light wrappers for POSIX i/o functions
- * Time-stamp: <2010-11-13 08:07:43 njk>
+ * Time-stamp: <2010-11-13 08:22:48 njk>
  *
  * (c) 2010 Nicholas J. Kain <njkain at gmail dot com>
  * All rights reserved.
@@ -30,6 +30,7 @@
 #ifndef NCM_IO_H_
 #define NCM_IO_H_
 
+int safe_read(int fd, char *buf, int len);
 int safe_write(int fd, const char *buf, int len);
 
 #endif /* NCM_IO_H_ */
diff --git a/ndhc/clientpacket.c b/ndhc/clientpacket.c
index a4eb325..d52b9a3 100644
--- a/ndhc/clientpacket.c
+++ b/ndhc/clientpacket.c
@@ -41,26 +41,31 @@
 #include "options.h"
 #include "dhcpc.h"
 #include "log.h"
+#include "io.h"
 
 /* Create a random xid */
 uint32_t random_xid(void)
 {
     static int initialized;
-    if (!initialized) {
-        int fd;
-        uint32_t seed;
+    if (initialized)
+        return rand();
 
-        fd = open("/dev/urandom", O_RDONLY);
-        if (fd == -1 || read(fd, &seed, sizeof seed) < 0) {
-                log_warning("Could not load seed from /dev/urandom: %s",
-                            strerror(errno));
-                seed = time(0);
+    uint32_t seed;
+    int fd = open("/dev/urandom", O_RDONLY);
+    if (fd != -1) {
+        int r = safe_read(fd, (char *)&seed, sizeof seed);
+        if (r == -1) {
+            log_warning("Could not read /dev/urandom: %s", strerror(errno));
+            close(fd);
+            seed = time(0);
         }
-        if (fd != -1)
-                close(fd);
-        srand(seed);
-        initialized++;
+    } else {
+        log_warning("Could not open /dev/urandom: %s",
+                    strerror(errno));
+        seed = time(0);
     }
+    srand(seed);
+    initialized = 1;
     return rand();
 }
 
@@ -178,24 +183,15 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
     struct udp_dhcp_packet packet;
     uint32_t source, dest;
     uint16_t check;
-
-    ssize_t len = 0;
-    const ssize_t header_size = sizeof(struct iphdr) + sizeof(struct udphdr);
-    const ssize_t packet_size = sizeof(struct udp_dhcp_packet);
+    const int header_size = sizeof(struct iphdr) + sizeof(struct udphdr);
+    const int packet_size = sizeof(struct udp_dhcp_packet);
 
     memset(&packet, 0, packet_size);
-    while (len < packet_size) {
-        ssize_t r = read(fd, ((char *)&packet) + len, packet_size - len);
-        if (r == 0)
-            break;
-        if (r == -1) {
-            if (errno == EINTR)
-                continue;
-            log_line("get_raw_packet: read error %s", strerror(errno));
-            usleep(500000); /* possible down interface, looping condition */
-            return -1;
-        }
-        len += r;
+    int len = safe_read(fd, (char *)&packet, packet_size);
+    if (len == -1) {
+        log_line("get_raw_packet: read error %s", strerror(errno));
+        usleep(500000); /* possible down interface, looping condition */
+        return -1;
     }
 
     if (len < header_size) {
diff --git a/ndhc/packet.c b/ndhc/packet.c
index 1fc5763..a03c4c9 100644
--- a/ndhc/packet.c
+++ b/ndhc/packet.c
@@ -48,9 +48,9 @@ int get_packet(struct dhcpMessage *packet, int fd)
     unsigned char *vendor;
 
     memset(packet, 0, sizeof(struct dhcpMessage));
-    bytes = read(fd, packet, sizeof(struct dhcpMessage));
-    if (bytes < 0) {
-	log_line("couldn't read on listening socket, ignoring");
+    bytes = safe_read(fd, (char *)packet, sizeof(struct dhcpMessage));
+    if (bytes == -1) {
+	log_line("read on listen socket failed: %s", strerror(errno));
 	return -1;
     }