Provide better commentary.

diff --git a/common.c b/common.c
index 5ba3deebe3fbc282c9ab07e0dea365cc94373854..9b803226b08e495432757c02310b6407eeac2a71 100644 (file)
--- a/common.c
+++ b/common.c
@@ -397,7 +397,7 @@ recvmsg_realloc(int fd, struct msghdr *msg, int flags)
        iov = &msg->msg_iov[msg->msg_iovlen - 1];
 
        for (;;) {
-               msg->msg_flags = 0;
+               /* Passing MSG_TRUNC should return the actual size needed. */
                slen = recvmsg(fd, msg, flags | MSG_PEEK | MSG_TRUNC);
                if (slen == -1)
                        return -1;
@@ -406,9 +406,9 @@ recvmsg_realloc(int fd, struct msghdr *msg, int flags)
 
                len = (size_t)slen;
 
-               /* Some kernels return the truncated size, but others
-                * can return the actual size needed because
-                * we passed MSG_TRUNC above. */
+               /* Some kernels return the size of the receive buffer
+                * on truncation, not the actual size needed.
+                * So grow the buffer and try again. */
                if (iov->iov_len == len)
                        len = roundup(len + 1, IOVEC_BUFSIZ);
                else if (iov->iov_len > len)
@@ -419,7 +419,6 @@ recvmsg_realloc(int fd, struct msghdr *msg, int flags)
                iov->iov_len = len;
        }
 
-       msg->msg_flags = 0;
        slen = recvmsg(fd, msg, flags);
        if (msg->msg_flags & MSG_TRUNC) {
                /* This should not be possible ... */