Switch to using a socket for ndhc/sockd IPC so that fd passing works.

ndhc/ndhc.c

@@ -343,10 +343,8 @@ int pToNdhcW;
 int pToIfchR;
 int pToIfchW;
 
-int psToNdhcR;
-int psToNdhcW;
-int pToSockdR;
-int pToSockdW;
+int sockdSock[2];
+int sockdPipe[2];
 
 static void create_ifch_ipc_pipes(void) {
     int niPipe[2];
@@ -371,22 +369,10 @@ static void create_ifch_ipc_pipes(void) {
 }
 
 static void create_sockd_ipc_pipes(void) {
-    int nsPipe[2];
-    int snPipe[2];
-
-    if (pipe2(nsPipe, 0))
-        suicide("FATAL - can't create ndhc -> ndhc-sockd pipe: %s",
-                strerror(errno));
-    psToNdhcR = nsPipe[0];
-    psToNdhcW = nsPipe[1];
-    if (pipe2(snPipe, 0))
-        suicide("FATAL - can't create ndhc-sockd -> ndhc pipe: %s",
-                strerror(errno));
-    if (fcntl(snPipe[0], F_SETFL, fcntl(snPipe[0], F_GETFL) | O_NONBLOCK) < 0)
-        suicide("FATAL - failed to set ndhc-sockd -> ndhc read-side nonblocking: %s",
-                strerror(errno));
-    pToSockdR = snPipe[0];
-    pToSockdW = snPipe[1];
+    if (pipe2(sockdPipe, 0))
+        suicide("FATAL - can't create ndhc/sockd pipe: %s", strerror(errno));
+    if (socketpair(AF_UNIX, SOCK_DGRAM, 0, sockdSock) < 0)
+        suicide("FATAL - can't create ndhc/sockd socket: %s", strerror(errno));
 }
 
 static void spawn_ifch(void)
@@ -411,14 +397,14 @@ static void spawn_sockd(void)
     create_sockd_ipc_pipes();
     pid_t sockd_pid = fork();
     if (sockd_pid == 0) {
-        close(psToNdhcR);
-        close(pToSockdW);
+        close(sockdPipe[0]);
+        close(sockdSock[0]);
         // Don't share the RNG state with the master process.
         nk_random_u32_init(&cs.rnd32_state);
         sockd_main();
     } else if (sockd_pid > 0) {
-        close(pToSockdR);
-        close(psToNdhcW);
+        close(sockdSock[1]);
+        close(sockdPipe[1]);
     } else
         suicide("failed to fork ndhc-sockd: %s", strerror(errno));
 }

ndhc/ndhc.h

@@ -71,10 +71,8 @@ extern int pToIfchR;
 extern int pToIfchW;
 extern int pToNdhcR;
 extern int pToNdhcW;
-extern int psToNdhcR;
-extern int psToNdhcW;
-extern int pToSockdR;
-extern int pToSockdW;
+extern int sockdSock[2];
+extern int sockdPipe[2];
 extern char state_dir[PATH_MAX];
 extern char chroot_dir[PATH_MAX];
 extern char resolv_conf_d[PATH_MAX];

ndhc/sockd.c

@@ -70,7 +70,7 @@ int request_sockd_fd(char *buf, size_t buflen, char *response)
 {
     if (!buflen)
         return -1;
-    ssize_t r = safe_write(pToSockdW, buf, buflen);
+    ssize_t r = safe_write(sockdSock[0], buf, buflen);
     if (r < 0 || (size_t)r != buflen)
         suicide("%s: (%s) write failed: %d", client_config.interface,
                 __func__, r);
@@ -87,7 +87,7 @@ int request_sockd_fd(char *buf, size_t buflen, char *response)
         .msg_controllen = sizeof control
     };
   retry:
-    r = recvmsg(psToNdhcR, &msg, 0);
+    r = recvmsg(sockdSock[0], &msg, 0);
     if (r == 0) {
         suicide("%s: (%s) recvmsg received EOF", client_config.interface,
                 __func__);
@@ -405,7 +405,7 @@ static void xfer_fd(int fd, char cmd)
     *cmsg_fd = fd;
     msg.msg_controllen = cmsg->cmsg_len;
   retry:
-    if (sendmsg(psToNdhcW, &msg, 0) < 0) {
+    if (sendmsg(sockdSock[1], &msg, 0) < 0) {
         if (errno == EINTR)
             goto retry;
         suicide("%s: (%s) sendmsg failed: %s", client_config.interface,
@@ -451,7 +451,8 @@ static void process_client_pipe(void)
         suicide("%s: (%s) receive buffer exhausted", client_config.interface,
                 __func__);
 
-    int r = safe_read(pToSockdR, buf + buflen, sizeof buf - buflen);
+    int r = safe_recv(sockdSock[1], buf + buflen, sizeof buf - buflen,
+                      MSG_DONTWAIT);
     if (r == 0) {
         // Remote end hung up.
         exit(EXIT_SUCCESS);
@@ -474,7 +475,7 @@ static void do_sockd_work(void)
     if (enforce_seccomp_sockd())
         log_line("sockd seccomp filter cannot be installed");
 
-    epoll_add(epollfd, pToSockdR);
+    epoll_add(epollfd, sockdSock[1]);
     epoll_add(epollfd, signalFd);
 
     for (;;) {
@@ -487,7 +488,7 @@ static void do_sockd_work(void)
         }
         for (int i = 0; i < r; ++i) {
             int fd = events[i].data.fd;
-            if (fd == pToSockdR)
+            if (fd == sockdSock[1])
                 process_client_pipe();
             else if (fd == signalFd)
                 signal_dispatch();