device: Flush buffer to client when remote side unexpectedly terminates connection

2 files changed, 16 insertions, 2 deletions

diff --git a/src/client.c b/src/client.c
index a9c986a..bbdac84 100644
--- a/src/client.c
+++ b/src/client.c
@@ -113,7 +113,8 @@ int client_write(struct mux_client *client, void *buffer, uint32_t len)
         sret = send(client->fd, buffer, len, 0);
         if (sret < 0) {
                 if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
-                        usbmuxd_log(LL_ERROR, "ERROR: client_write: fd %d not ready for writing", client->fd);
+                        usbmuxd_log(LL_DEBUG, "client_write: fd %d not ready for writing", client->fd);
+                        sret = 0;
                 } else {
                         usbmuxd_log(LL_ERROR, "ERROR: client_write: sending to fd %d failed: %s", client->fd, strerror(errno));
                 }
diff --git a/src/device.c b/src/device.c
index d5cf9f0..3edaea0 100644
--- a/src/device.c
+++ b/src/device.c
@@ -32,6 +32,7 @@
 #include <stdint.h>
 #include <inttypes.h>
 #include <pthread.h>
+#include <unistd.h>
 #include "device.h"
 #include "client.h"
 #include "preflight.h"
@@ -314,10 +315,21 @@ static void connection_teardown(struct mux_connection *conn)
                 } else {
                         conn->state = CONN_DEAD;
                         if((conn->events & POLLOUT) && conn->ib_size > 0){
+                                usbmuxd_log(LL_DEBUG, "%s: flushing buffer to client (%u bytes)", __func__, conn->ib_size);
+                                uint64_t tm_last = mstime64();
                                 while(1){
                                         size = client_write(conn->client, conn->ib_buf, conn->ib_size);
-                                        if(size <= 0) {
+                                        if(size < 0) {
+                                                usbmuxd_log(LL_ERROR, "%s: aborting buffer flush to client after error.", __func__);
                                                 break;
+                                        } else if (size == 0) {
+                                                uint64_t tm_now = mstime64();
+                                                if (tm_now - tm_last > 1000) {
+                                                        usbmuxd_log(LL_ERROR, "%s: aborting buffer flush to client after unsuccessfully attempting for %dms.", __func__, (int)(tm_now - tm_last));
+                                                        break;
+                                                }
+                                                usleep(10000);
+                                                continue;
                                         }
                                         if(size == (int)conn->ib_size) {
                                                 conn->ib_size = 0;
@@ -326,6 +338,7 @@ static void connection_teardown(struct mux_connection *conn)
                                                 conn->ib_size -= size;
                                                 memmove(conn->ib_buf, conn->ib_buf + size, conn->ib_size);
                                         }
+                                        tm_last = mstime64();
                                 }
                         }
                         client_close(conn->client);