From 2e3c504cc50dad35ecc6a97434309b5e8b09301c Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Fri, 6 Nov 2020 18:47:51 -0500
Subject: [PATCH] Add and use safe_ftruncate() wrapper.

---
 src/ifchd.c     | 17 +++++++----------
 src/leasefile.c | 31 ++++++++++++++-----------------
 src/lib/io.c    | 17 +++++++++++++----
 src/nk/io.h     |  1 +
 4 files changed, 35 insertions(+), 31 deletions(-)

diff --git a/src/ifchd.c b/src/ifchd.c
index e5def3a..ff96cab 100644
--- a/src/ifchd.c
+++ b/src/ifchd.c
@@ -181,21 +181,18 @@ static int write_resolve_conf(void)
 
     off = lseek(resolv_conf_fd, 0, SEEK_CUR);
     if (off < 0) {
-        log_line("write_resolve_conf: lseek returned error: %s",
-                strerror(errno));
+        log_line("%s: (%s) lseek returned error: %s", client_config.interface,
+                 __func__, strerror(errno));
         return -1;
     }
-  retry:
-    if (ftruncate(resolv_conf_fd, off) < 0) {
-        if (errno == EINTR)
-            goto retry;
-        log_line("write_resolve_conf: ftruncate returned error: %s",
-                 strerror(errno));
+    if (safe_ftruncate(resolv_conf_fd, off) < 0) {
+        log_line("%s: (%s) ftruncate returned error: %s", client_config.interface,
+                 __func__, strerror(errno));
         return -1;
     }
     if (fsync(resolv_conf_fd) < 0) {
-        log_line("write_resolve_conf: fsync returned error: %s",
-                 strerror(errno));
+        log_line("%s: (%s) fsync returned error: %s", client_config.interface,
+                 __func__, strerror(errno));
         return -1;
     }
     return 0;
diff --git a/src/leasefile.c b/src/leasefile.c
index c7bba88..17637bb 100644
--- a/src/leasefile.c
+++ b/src/leasefile.c
@@ -62,15 +62,14 @@ void open_leasefile(void)
     get_leasefile_path(leasefile, sizeof leasefile, client_config.interface);
     leasefilefd = open(leasefile, O_WRONLY|O_TRUNC|O_CREAT, 0644);
     if (leasefilefd < 0)
-        suicide("%s: Failed to create lease file '%s': %s",
-                client_config.interface, leasefile, strerror(errno));
+        suicide("%s: (%s) Failed to create lease file '%s': %s",
+                client_config.interface, __func__, leasefile, strerror(errno));
 }
 
 void write_leasefile(struct in_addr ipnum)
 {
     char ip[INET_ADDRSTRLEN];
     char out[INET_ADDRSTRLEN*2];
-    ssize_t ret;
     if (leasefilefd < 0) {
         log_error("%s: (%s) leasefile fd < 0; no leasefile will be written",
                   client_config.interface, __func__);
@@ -83,23 +82,21 @@ void write_leasefile(struct in_addr ipnum)
                   client_config.interface, __func__, olen);
         return;
     }
-  retry_trunc:
-    ret = ftruncate(leasefilefd, 0);
-    switch (ret) {
-        default: break;
-        case -1:
-            if (errno == EINTR)
-                goto retry_trunc;
-            log_warning("%s: Failed to truncate lease file: %s",
-                        client_config.interface, strerror(errno));
-            return;
+    if (safe_ftruncate(leasefilefd, 0)) {
+        log_warning("%s: (%s) Failed to truncate lease file: %s",
+                    client_config.interface, __func__, strerror(errno));
+        return;
+    }
+    if (lseek(leasefilefd, 0, SEEK_SET) == (off_t)-1) {
+        log_warning("%s: (%s) Failed to seek to start of lease file: %s",
+                    client_config.interface, __func__, strerror(errno));
+        return;
     }
-    lseek(leasefilefd, 0, SEEK_SET);
     size_t outlen = strlen(out);
-    ret = safe_write(leasefilefd, out, outlen);
+    ssize_t ret = safe_write(leasefilefd, out, outlen);
     if (ret < 0 || (size_t)ret != outlen)
-        log_warning("%s: Failed to write ip to lease file.",
-                    client_config.interface);
+        log_warning("%s: (%s) Failed to write ip to lease file.",
+                    client_config.interface, __func__);
     else
         fsync(leasefilefd);
 }
diff --git a/src/lib/io.c b/src/lib/io.c
index f842421..bdb93be 100644
--- a/src/lib/io.c
+++ b/src/lib/io.c
@@ -122,10 +122,19 @@ ssize_t safe_recv(int fd, char *buf, size_t len, int flags)
 ssize_t safe_recvmsg(int fd, struct msghdr *msg, int flags)
 {
     ssize_t r;
-  retry:
-    r = recvmsg(fd, msg, flags);
-    if (r < 0 && errno == EINTR)
-        goto retry;
+    for (;;) {
+        r = recvmsg(fd, msg, flags);
+        if (r >= 0 || errno != EINTR) break;
+    }
     return r;
 }
 
+int safe_ftruncate(int fd, off_t length)
+{
+    int r;
+    for (;;) {
+        r = ftruncate(fd, length);
+        if (!r || errno != EINTR) break;
+    }
+    return r;
+}
diff --git a/src/nk/io.h b/src/nk/io.h
index 3ecc148..985522d 100644
--- a/src/nk/io.h
+++ b/src/nk/io.h
@@ -37,5 +37,6 @@ ssize_t safe_sendto(int fd, const char *buf, size_t len, int flags,
                     const struct sockaddr *dest_addr, socklen_t addrlen);
 ssize_t safe_recv(int fd, char *buf, size_t len, int flags);
 ssize_t safe_recvmsg(int fd, struct msghdr *msg, int flags);
+int safe_ftruncate(int fd, off_t length);
 
 #endif /* NCM_IO_H_ */