Merge pull request #3202 from poettering/socket-fixes

don't reopen socket fds when reloading the daemon

src/basic/io-util.c

@@ -33,6 +33,11 @@ int flush_fd(int fd) {
                 .events = POLLIN,
         };
 
+        /* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything
+         * read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read
+         * (due to IP packet checksum mismatches), hence this function is only safe to be non-blocking if the fd used
+         * was set to non-blocking too. */
+
         for (;;) {
                 char buf[LINE_MAX];
                 ssize_t l;

src/basic/socket-util.c

@@ -23,6 +23,7 @@
 #include <net/if.h>
 #include <netdb.h>
 #include <netinet/ip.h>
+#include <poll.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -970,3 +971,42 @@ fallback:
 
         return (ssize_t) k;
 }
+
+int flush_accept(int fd) {
+
+        struct pollfd pollfd = {
+                .fd = fd,
+                .events = POLLIN,
+        };
+        int r;
+
+
+        /* Similar to flush_fd() but flushes all incoming connection by accepting them and immediately closing them. */
+
+        for (;;) {
+                int cfd;
+
+                r = poll(&pollfd, 1, 0);
+                if (r < 0) {
+                        if (errno == EINTR)
+                                continue;
+
+                        return -errno;
+
+                } else if (r == 0)
+                        return 0;
+
+                cfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);
+                if (cfd < 0) {
+                        if (errno == EINTR)
+                                continue;
+
+                        if (errno == EAGAIN)
+                                return 0;
+
+                        return -errno;
+                }
+
+                close(cfd);
+        }
+}

src/basic/socket-util.h

@@ -135,6 +135,8 @@ int receive_one_fd(int transport_fd, int flags);
 
 ssize_t next_datagram_size_fd(int fd);
 
+int flush_accept(int fd);
+
 #define CMSG_FOREACH(cmsg, mh)                                          \
         for ((cmsg) = CMSG_FIRSTHDR(mh); (cmsg); (cmsg) = CMSG_NXTHDR((mh), (cmsg)))