Add/improve comment, shorten some usage texts. No code changes.

2 files changed, 21 insertions, 2 deletions

diff --git a/ipsvd/tcpudp.c b/ipsvd/tcpudp.c
index 9f098c32e..66f44e9a6 100644
--- a/ipsvd/tcpudp.c
+++ b/ipsvd/tcpudp.c
@@ -331,12 +331,31 @@ int tcpudpsvd_main(int argc, char **argv)
                  * to ones coming from this remote IP. */
                 xconnect(0, &remote.sa, sa_len);
         /* hole? at this point we have no wildcard udp socket...
-         * can this cause clients to get "port unreachable" icmp? */
+         * can this cause clients to get "port unreachable" icmp?
+         * Yup, time window is very small, but it exists (is it?) */
                 /* Open new non-connected UDP socket for further clients */
                 sock = xsocket(lsa->sa.sa_family, tcp ? SOCK_STREAM : SOCK_DGRAM, 0);
                 setsockopt_reuseaddr(sock);
                 xbind(sock, &lsa->sa, sa_len);
                 socket_want_pktinfo(sock);
+
+                /* Doesn't work:
+                 * we cannot replace fd #0 - we will lose pending packet
+                 * which is already buffered for us! And we cannot use fd #1
+                 * instead - it will "intercept" all following packets, but child
+                 * do not expect data coming *from fd #1*! */
+#if 0
+                /* Make it so that local addr is fixed to localp->sa
+                 * and we don't accidentally accept packets to other local IPs. */
+                /* NB: we possibly bind to the _very_ same_ address & port as the one
+                 * already bound in parent! This seems to work in Linux.
+                 * (otherwise we can move socket to fd #0 only if bind succeeds) */
+                close(0);
+                set_nport(localp, htons(local_port));
+                xmove_fd(xsocket(localp->sa.sa_family, SOCK_DGRAM, 0), 0);
+                setsockopt_reuseaddr(0); /* crucial */
+                xbind(0, &localp->sa, localp->len);
+#endif
         }
 
         pid = fork();
diff --git a/ipsvd/udp_io.c b/ipsvd/udp_io.c
index 2efc15913..592d98b58 100644
--- a/ipsvd/udp_io.c
+++ b/ipsvd/udp_io.c
@@ -95,7 +95,7 @@ send_to_from(int fd, void *buf, size_t len, int flags,
 
 /* NB: this will never set port# in 'to'!
  * _Only_ IP/IPv6 address part of 'to' is _maybe_ modified.
- * Typical usage is to preinit it with "default" value
+ * Typical usage is to preinit 'to' with "default" value
  * before calling recv_from_to(). */
 ssize_t
 recv_from_to(int fd, void *buf, size_t len, int flags,