Better handle read()s of multiple frames from TNC

Implement better handling of situations when read() captures multiple
TNC frames; ensure each frame is handled in src/server.c, function
handle_iface(), to ensure packets aren't ignored before the next
select() call

include/patty/ax25/if.h

@@ -82,6 +82,8 @@ int patty_ax25_if_promisc_add(patty_ax25_if *iface,
 int patty_ax25_if_promisc_delete(patty_ax25_if *iface,
                                  int fd);
 
+ssize_t patty_ax25_if_pending(patty_ax25_if *iface);
+
 ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
                            void **buf);
 

include/patty/kiss.h

@@ -39,6 +39,8 @@ void patty_kiss_tnc_destroy(patty_kiss_tnc *tnc);
 
 size_t patty_kiss_tnc_dropped(patty_kiss_tnc *tnc);
 
+ssize_t patty_kiss_tnc_pending(patty_kiss_tnc *tnc);
+
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
                             void *buf,
                             size_t len,

src/if.c

@@ -336,6 +336,10 @@ static int handle_promisc_frame(uint32_t key,
     return patty_kiss_tnc_send(tnc, frame->buf, frame->len, 0);
 }
 
+ssize_t patty_ax25_if_pending(patty_ax25_if *iface) {
+    return patty_kiss_tnc_pending(iface->tnc);
+}
+
 ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
                            void **buf) {
     ssize_t readlen;
@@ -347,6 +351,8 @@ ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
                                        iface->rx_bufsz,
                                        &port)) < 0) {
         goto error_kiss_tnc_recv;
+    } else if (readlen == 0) {
+        goto done;
     }
 
     *buf = iface->rx_buf;
@@ -364,6 +370,7 @@ ssize_t patty_ax25_if_recv(patty_ax25_if *iface,
         goto error_handle_promisc_frame;
     }
 
+done:
     return readlen;
 
 error_handle_promisc_frame:

src/kiss.c

@@ -109,6 +109,18 @@ size_t patty_kiss_tnc_dropped(patty_kiss_tnc *tnc) {
     return tnc->dropped;
 }
 
+ssize_t patty_kiss_tnc_pending(patty_kiss_tnc *tnc) {
+    if (tnc->readlen < 0) {
+        return -1;
+    }
+
+    if (tnc->offset == 0) {
+        return 0;
+    }
+
+    return tnc->readlen - tnc->offset;
+}
+
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
                             void *buf,
                             size_t len,

src/server.c

@@ -1342,6 +1342,7 @@ static int handle_iface(patty_ax25_server *server, patty_ax25_if *iface) {
         goto done;
     }
 
+    do {
         if ((readlen = patty_ax25_if_recv(iface, &buf)) < 0) {
             goto error_io;
         } else if (readlen == 0) {
@@ -1353,6 +1354,7 @@ static int handle_iface(patty_ax25_server *server, patty_ax25_if *iface) {
         if (handle_frame(server, iface, buf, readlen) < 0) {
             goto error_io;
         }
+    } while (patty_ax25_if_pending(iface));
 
 done:
     return 0;