Optimise recvmsg_realloc.

diff --git a/common.c b/common.c
index 8d1b5a8ce011b7c63a13f4d94409780bea5d6a36..5ba3deebe3fbc282c9ab07e0dea365cc94373854 100644 (file)
--- a/common.c
+++ b/common.c
@@ -31,6 +31,7 @@
 #include <sys/sysmacros.h>
 #endif
 
+#include <assert.h>
 #include <ctype.h>
 #include <err.h>
 #include <errno.h>
@@ -381,52 +382,49 @@ read_hwaddr_aton(uint8_t **data, const char *path)
        return len;
 }
 
-static void *
-iovec_realloc(struct iovec *iov, size_t size)
-{
-
-       if (iov->iov_len < size) {
-               void *n;
-
-               if ((n = realloc(iov->iov_base, size)) == NULL)
-                       return NULL;
-               iov->iov_base = n;
-               iov->iov_len = size;
-       }
-       return iov->iov_base;
-}
-
 ssize_t
 recvmsg_realloc(int fd, struct msghdr *msg, int flags)
 {
-       ssize_t len;
        struct iovec *iov;
+       ssize_t slen;
+       size_t len;
+       void *n;
+
+       assert(msg != NULL);
+       assert((flags & (MSG_PEEK | MSG_TRUNC)) == 0);
 
        /* Assume we are reallocing the last iovec. */
        iov = &msg->msg_iov[msg->msg_iovlen - 1];
 
        for (;;) {
                msg->msg_flags = 0;
-               len = recvmsg(fd, msg, flags | MSG_PEEK | MSG_TRUNC);
-               if (len == -1)
+               slen = recvmsg(fd, msg, flags | MSG_PEEK | MSG_TRUNC);
+               if (slen == -1)
                        return -1;
                if (!(msg->msg_flags & MSG_TRUNC))
                        break;
 
-               /* Some kernels return the truncated size. */
-               if (iov->iov_len == (size_t)len) {
-                       size_t nl;
+               len = (size_t)slen;
 
-                       nl = (size_t)roundup(len + 1, IOVEC_BUFSIZ);
-                       if (iovec_realloc(iov, nl) == NULL)
-                               return -1;
-               } else {
-                       if (iovec_realloc(iov, (size_t)len) == NULL)
-                               return -1;
+               /* Some kernels return the truncated size, but others
+                * can return the actual size needed because
+                * we passed MSG_TRUNC above. */
+               if (iov->iov_len == len)
+                       len = roundup(len + 1, IOVEC_BUFSIZ);
+               else if (iov->iov_len > len)
                        break;
-               }
+               if ((n = realloc(iov->iov_base, len)) == NULL)
+                       return -1;
+               iov->iov_base = n;
+               iov->iov_len = len;
        }
 
-       len = recvmsg(fd, msg, flags);
-       return msg->msg_flags & MSG_TRUNC ? -1 : len;
+       msg->msg_flags = 0;
+       slen = recvmsg(fd, msg, flags);
+       if (msg->msg_flags & MSG_TRUNC) {
+               /* This should not be possible ... */
+               errno = ENOBUFS;
+               return -1;
+       }
+       return slen;
 }