The last part of udp_sock_handler() does the actual sending of frames
to the tap interface. For pasta that's just a call to
udp_tap_send_pasta() but for passt, it's moderately complex and open
coded.
For symmetry, move the passt send path into its own function,
udp_tap_send_passt(). This will make it easier to abstract the tap
interface in future (e.g. when we want to add vhost-user).
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
udp.c | 130 ++++++++++++++++++++++++++++++++--------------------------
1 file changed, 72 insertions(+), 58 deletions(-)
diff --git a/udp.c b/udp.c
index a27fe88..7281bc3 100644
--- a/udp.c
+++ b/udp.c
@@ -812,6 +812,73 @@ static void udp_tap_send_pasta(const struct ctx *c, struct mmsghdr
*mmh,
}
}
+/**
+ * udp_tap_send_passt() - Send datagrams to the passt tap interface
+ * @c: Execution context
+ * @mmh: Array of message headers to send
+ * @n: Number of message headers to send
+ *
+ * #syscalls:passt sendmmsg sendmsg
+ */
+static void udp_tap_send_passt(const struct ctx *c, struct mmsghdr *mmh, int n)
+{
+ struct msghdr *last_mh;
+ ssize_t missing = 0;
+ size_t msg_len = 0;
+ unsigned int i;
+ int ret;
+
+ ret = sendmmsg(c->fd_tap, mmh, n, MSG_NOSIGNAL | MSG_DONTWAIT);
+ if (ret <= 0)
+ return;
+
+ /* If we lose some messages to sendmmsg() here, fine, it's UDP. However,
+ * the last message needs to be delivered completely, otherwise qemu
+ * will fail to reassemble the next message and close the connection. Go
+ * through headers from the last sent message, counting bytes, and, if
+ * and as soon as we see more bytes than sendmmsg() sent, re-send the
+ * rest with a blocking call.
+ *
+ * In pictures, given this example:
+ *
+ * iov #0 iov #1 iov #2 iov #3
+ * tap_mmh[ret - 1].msg_hdr: .... ...... ..... ......
+ * tap_mmh[ret - 1].msg_len: 7 .... ...
+ *
+ * when 'msglen' reaches: 10 ^
+ * and 'missing' below is: 3 ---
+ *
+ * re-send everything from here: ^-- ----- ------
+ */
+ last_mh = &mmh[ret - 1].msg_hdr;
+ for (i = 0; i < last_mh->msg_iovlen; i++) {
+ if (missing <= 0) {
+ msg_len += last_mh->msg_iov[i].iov_len;
+ missing = msg_len - mmh[ret - 1].msg_len;
+ }
+
+ if (missing > 0) {
+ uint8_t **iov_base;
+ int first_offset;
+
+ iov_base = (uint8_t **)&last_mh->msg_iov[i].iov_base;
+ first_offset = last_mh->msg_iov[i].iov_len - missing;
+ *iov_base += first_offset;
+ last_mh->msg_iov[i].iov_len = missing;
+
+ last_mh->msg_iov = &last_mh->msg_iov[i];
+
+ if (sendmsg(c->fd_tap, last_mh, MSG_NOSIGNAL) < 0)
+ debug("UDP: %li bytes to tap missing", missing);
+
+ *iov_base -= first_offset;
+ break;
+ }
+ }
+
+ pcapmm(mmh, ret);
+}
+
/**
* udp_sock_handler() - Handle new data from socket
* @c: Execution context
@@ -820,16 +887,14 @@ static void udp_tap_send_pasta(const struct ctx *c, struct mmsghdr
*mmh,
* @now: Current timestamp
*
* #syscalls recvmmsg
- * #syscalls:passt sendmmsg sendmsg
*/
void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
const struct timespec *now)
{
in_port_t dstport = ref.r.p.udp.udp.port;
- ssize_t n, msg_len = 0, missing = 0;
struct mmsghdr *tap_mmh, *sock_mmh;
- int msg_bufs = 0, msg_i = 0, ret;
- struct msghdr *last_mh;
+ int msg_bufs = 0, msg_i = 0;
+ ssize_t n, msg_len = 0;
struct iovec *tap_iov;
unsigned int i;
@@ -879,61 +944,10 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref,
uint32_t events,
}
tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs;
- if (c->mode == MODE_PASTA) {
+ if (c->mode == MODE_PASTA)
udp_tap_send_pasta(c, tap_mmh, msg_i + 1);
- return;
- }
-
- ret = sendmmsg(c->fd_tap, tap_mmh, msg_i + 1,
- MSG_NOSIGNAL | MSG_DONTWAIT);
- if (ret <= 0)
- return;
-
- /* If we lose some messages to sendmmsg() here, fine, it's UDP. However,
- * the last message needs to be delivered completely, otherwise qemu
- * will fail to reassemble the next message and close the connection. Go
- * through headers from the last sent message, counting bytes, and, if
- * and as soon as we see more bytes than sendmmsg() sent, re-send the
- * rest with a blocking call.
- *
- * In pictures, given this example:
- *
- * iov #0 iov #1 iov #2 iov #3
- * tap_mmh[ret - 1].msg_hdr: .... ...... ..... ......
- * tap_mmh[ret - 1].msg_len: 7 .... ...
- *
- * when 'msglen' reaches: 10 ^
- * and 'missing' below is: 3 ---
- *
- * re-send everything from here: ^-- ----- ------
- */
- last_mh = &tap_mmh[ret - 1].msg_hdr;
- for (i = 0, msg_len = 0; i < last_mh->msg_iovlen; i++) {
- if (missing <= 0) {
- msg_len += last_mh->msg_iov[i].iov_len;
- missing = msg_len - tap_mmh[ret - 1].msg_len;
- }
-
- if (missing > 0) {
- uint8_t **iov_base;
- int first_offset;
-
- iov_base = (uint8_t **)&last_mh->msg_iov[i].iov_base;
- first_offset = last_mh->msg_iov[i].iov_len - missing;
- *iov_base += first_offset;
- last_mh->msg_iov[i].iov_len = missing;
-
- last_mh->msg_iov = &last_mh->msg_iov[i];
-
- if (sendmsg(c->fd_tap, last_mh, MSG_NOSIGNAL) < 0)
- debug("UDP: %li bytes to tap missing", missing);
-
- *iov_base -= first_offset;
- break;
- }
- }
-
- pcapmm(tap_mmh, ret);
+ else
+ udp_tap_send_passt(c, tap_mmh, msg_i + 1);
}
/**
--
2.39.0