[PATCH v2 1/4] tap: Clean up tap reset path

[David Gibson <david@gibson.dropbear.id.au>]

In tap_handler() if we get an error on the tap device or socket, we use
tap_sock_init() to re-initialise it.  However, what we actually need for
this reset case has remarkably little in common with the case where we're
initialising for the first time:
    * Re-initialising the packet pools is unnecessary
    * The case of a passed in fd (--fd) isn't relevant
    * We don't even call this for pasta mode
    * We will never re-call tap_sock_unix_init() because we never clear
      fd_tap_listen

In fact the only thing we do in tap_sock_init() relevant to the reset case
is to remove the fd from the epoll and close it... which isn't used in the
first initialisation case.

So make a new tap_sock_reset() function just for this case, and simplify
tap_sock_init() slightly as being used only for the first time case.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 tap.c | 52 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/tap.c b/tap.c
index e034f94..b4967d0 100644
--- a/tap.c
+++ b/tap.c
@@ -1236,19 +1236,14 @@ void tap_sock_init(struct ctx *c)
 		tap6_l4[i].p = PACKET_INIT(pool_l4, TAP_SEQS, pkt_buf, sz);
 	}
 
-	if (c->fd_tap != -1) {
-		if (c->one_off) {	/* Passed as --fd */
-			struct epoll_event ev = { 0 };
-
-			ev.data.fd = c->fd_tap;
-			ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
-			epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
-			return;
-		}
+	if (c->fd_tap != -1) { /* Passed as --fd */
+		struct epoll_event ev = { 0 };
+		ASSERT(c->one_off);
 
-		epoll_ctl(c->epollfd, EPOLL_CTL_DEL, c->fd_tap, NULL);
-		close(c->fd_tap);
-		c->fd_tap = -1;
+		ev.data.fd = c->fd_tap;
+		ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
+		epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
+		return;
 	}
 
 	if (c->mode == MODE_PASST) {
@@ -1259,6 +1254,26 @@ void tap_sock_init(struct ctx *c)
 	}
 }
 
+/**
+ * tap_sock_reset() - Handle closing or failure of connect AF_UNIX socket
+ * @c:		Execution context
+ */
+static void tap_sock_reset(struct ctx *c)
+{
+	if (c->one_off) {
+		info("Client closed connection, exiting");
+		exit(EXIT_SUCCESS);
+	}
+
+	if (c->mode == MODE_PASTA)
+		die("Error on tap device, exiting");
+
+	/* Close the connected socket, wait for a new connection */
+	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, c->fd_tap, NULL);
+	close(c->fd_tap);
+	c->fd_tap = -1;
+}
+
 /**
  * tap_handler() - Packet handler for AF_UNIX or tuntap file descriptor
  * @c:		Execution context
@@ -1276,15 +1291,6 @@ void tap_handler(struct ctx *c, int fd, uint32_t events,
 
 	if ((c->mode == MODE_PASST && tap_handler_passt(c, now)) ||
 	    (c->mode == MODE_PASTA && tap_handler_pasta(c, now)) ||
-	    (events & (EPOLLRDHUP | EPOLLHUP | EPOLLERR))) {
-		if (c->one_off) {
-			info("Client closed connection, exiting");
-			exit(EXIT_SUCCESS);
-		}
-
-		if (c->mode == MODE_PASTA)
-			die("Error on tap device, exiting");
-
-		tap_sock_init(c);
-	}
+	    (events & (EPOLLRDHUP | EPOLLHUP | EPOLLERR)))
+		tap_sock_reset(c);
 }
-- 
@@ -1236,19 +1236,14 @@ void tap_sock_init(struct ctx *c)
 		tap6_l4[i].p = PACKET_INIT(pool_l4, TAP_SEQS, pkt_buf, sz);
 	}
 
-	if (c->fd_tap != -1) {
-		if (c->one_off) {	/* Passed as --fd */
-			struct epoll_event ev = { 0 };
-
-			ev.data.fd = c->fd_tap;
-			ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
-			epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
-			return;
-		}
+	if (c->fd_tap != -1) { /* Passed as --fd */
+		struct epoll_event ev = { 0 };
+		ASSERT(c->one_off);
 
-		epoll_ctl(c->epollfd, EPOLL_CTL_DEL, c->fd_tap, NULL);
-		close(c->fd_tap);
-		c->fd_tap = -1;
+		ev.data.fd = c->fd_tap;
+		ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
+		epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
+		return;
 	}
 
 	if (c->mode == MODE_PASST) {
@@ -1259,6 +1254,26 @@ void tap_sock_init(struct ctx *c)
 	}
 }
 
+/**
+ * tap_sock_reset() - Handle closing or failure of connect AF_UNIX socket
+ * @c:		Execution context
+ */
+static void tap_sock_reset(struct ctx *c)
+{
+	if (c->one_off) {
+		info("Client closed connection, exiting");
+		exit(EXIT_SUCCESS);
+	}
+
+	if (c->mode == MODE_PASTA)
+		die("Error on tap device, exiting");
+
+	/* Close the connected socket, wait for a new connection */
+	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, c->fd_tap, NULL);
+	close(c->fd_tap);
+	c->fd_tap = -1;
+}
+
 /**
  * tap_handler() - Packet handler for AF_UNIX or tuntap file descriptor
  * @c:		Execution context
@@ -1276,15 +1291,6 @@ void tap_handler(struct ctx *c, int fd, uint32_t events,
 
 	if ((c->mode == MODE_PASST && tap_handler_passt(c, now)) ||
 	    (c->mode == MODE_PASTA && tap_handler_pasta(c, now)) ||
-	    (events & (EPOLLRDHUP | EPOLLHUP | EPOLLERR))) {
-		if (c->one_off) {
-			info("Client closed connection, exiting");
-			exit(EXIT_SUCCESS);
-		}
-
-		if (c->mode == MODE_PASTA)
-			die("Error on tap device, exiting");
-
-		tap_sock_init(c);
-	}
+	    (events & (EPOLLRDHUP | EPOLLHUP | EPOLLERR)))
+		tap_sock_reset(c);
 }
-- 
2.41.0