posix: implement MSG_PEEK handling in unix socket recv

JIRA: RTOS-877

lib/cbuffer.c

@@ -56,6 +56,17 @@ int _cbuffer_write(cbuffer_t *buf, const void *data, size_t sz)
 
 
 int _cbuffer_read(cbuffer_t *buf, void *data, size_t sz)
+{
+	int bytes = _cbuffer_peek(buf, data, sz);
+
+	buf->r = (buf->r + bytes) & (buf->sz - 1);
+	buf->full = 0;
+
+	return bytes;
+}
+
+
+int _cbuffer_peek(cbuffer_t *buf, void *data, size_t sz)
 {
 	int bytes = 0;
 
@@ -76,8 +87,5 @@ int _cbuffer_read(cbuffer_t *buf, void *data, size_t sz)
 		}
 	}
 
-	buf->r = (buf->r + bytes) & (buf->sz - 1);
-	buf->full = 0;
-
 	return bytes;
 }

lib/cbuffer.h

@@ -56,4 +56,6 @@ extern int _cbuffer_read(cbuffer_t *buf, void *data, size_t sz);
 extern int _cbuffer_write(cbuffer_t *buf, const void *data, size_t sz);
 
 
-#endif
+extern int _cbuffer_peek(cbuffer_t *buf, void *data, size_t sz);
+
+#endif

posix/unix.c

@@ -667,6 +667,7 @@ int unix_getsockopt(unsigned socket, int level, int optname, void *optval, sockl
 }
 
 
+/* TODO: peek fdpacks on MSG_PEEK */
 static ssize_t recv(unsigned socket, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *src_len, void *control, socklen_t *controllen)
 {
 	unixsock_t *s;
@@ -688,9 +689,15 @@ static ssize_t recv(unsigned socket, void *buf, size_t len, int flags, struct so
 		for (;;) {
 			proc_lockSet(&s->lock);
 			if (s->type == SOCK_STREAM) {
+				if (flags & MSG_PEEK) {
+					err = _cbuffer_peek(&s->buffer, buf, len);
+					proc_lockClear(&s->lock);
+					break;
+				}
 				err = _cbuffer_read(&s->buffer, buf, len);
 			}
 			else if (_cbuffer_avail(&s->buffer) > 0) { /* SOCK_DGRAM or SOCK_SEQPACKET */
+				/* TODO: handle MSG_PEEK */
 				_cbuffer_read(&s->buffer, &rlen, sizeof(rlen));
 				_cbuffer_read(&s->buffer, buf, err = min(len, rlen));