[PATCH 2/4] udp: Better factor IPv4 and IPv6 paths in udp_sock_handler()

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

Apart from which mh array they're operating on the recvmmsg() calls in
udp_sock_handler() are identical between the IPv4 and IPv6 paths, as are
some of the control structure updates.

By using some local variables to refer to the IP version specific control
arrays, make some more logic common between the IPv4 and IPv6 paths.  As
well as slightly reducing the code size, this makes it less likely that
we'll accidentally use the IPv4 arrays in the IPv6 path or vice versa as we
did in a recently fixed bug.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 udp.c | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/udp.c b/udp.c
index 99f9374..6a34e85 100644
--- a/udp.c
+++ b/udp.c
@@ -833,9 +833,10 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
 		      const struct timespec *now)
 {
 	ssize_t n, msg_len = 0, missing = 0;
+	struct mmsghdr *tap_mmh, *sock_mmh;
 	int msg_bufs = 0, msg_i = 0, ret;
-	struct mmsghdr *tap_mmh;
 	struct msghdr *last_mh;
+	struct iovec *tap_iov;
 	unsigned int i;
 
 	if (events == EPOLLERR)
@@ -847,34 +848,29 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
 	}
 
 	if (ref.r.p.udp.udp.v6) {
-		n = recvmmsg(ref.r.s, udp6_l2_mh_sock, UDP_TAP_FRAMES, 0, NULL);
-		if (n <= 0)
-			return;
-
-		udp6_l2_mh_tap[0].msg_hdr.msg_iov = &udp6_l2_iov_tap[0];
-
-		for (i = 0; i < (unsigned)n; i++) {
-			udp_sock_fill_data_v6(c, i, ref,
-					      &msg_i, &msg_bufs, &msg_len, now);
-		}
-
-		udp6_l2_mh_tap[msg_i].msg_hdr.msg_iovlen = msg_bufs;
 		tap_mmh = udp6_l2_mh_tap;
+		sock_mmh = udp6_l2_mh_sock;
+		tap_iov = udp6_l2_iov_tap;
 	} else {
-		n = recvmmsg(ref.r.s, udp4_l2_mh_sock, UDP_TAP_FRAMES, 0, NULL);
-		if (n <= 0)
-			return;
+		tap_mmh = udp4_l2_mh_tap;
+		sock_mmh = udp4_l2_mh_sock;
+		tap_iov = udp4_l2_iov_tap;
+	}
 
-		udp4_l2_mh_tap[0].msg_hdr.msg_iov = &udp4_l2_iov_tap[0];
+	n = recvmmsg(ref.r.s, sock_mmh, UDP_TAP_FRAMES, 0, NULL);
+	if (n <= 0)
+		return;
 
-		for (i = 0; i < (unsigned)n; i++) {
+	tap_mmh[0].msg_hdr.msg_iov = &tap_iov[0];
+	for (i = 0; i < (unsigned)n; i++) {
+		if (ref.r.p.udp.udp.v6)
+			udp_sock_fill_data_v6(c, i, ref,
+					      &msg_i, &msg_bufs, &msg_len, now);
+		else
 			udp_sock_fill_data_v4(c, i, ref,
 					      &msg_i, &msg_bufs, &msg_len, now);
-		}
-
-		udp4_l2_mh_tap[msg_i].msg_hdr.msg_iovlen = msg_bufs;
-		tap_mmh = udp4_l2_mh_tap;
 	}
+	tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs;
 
 	if (c->mode == MODE_PASTA)
 		return;
-- 
@@ -833,9 +833,10 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
 		      const struct timespec *now)
 {
 	ssize_t n, msg_len = 0, missing = 0;
+	struct mmsghdr *tap_mmh, *sock_mmh;
 	int msg_bufs = 0, msg_i = 0, ret;
-	struct mmsghdr *tap_mmh;
 	struct msghdr *last_mh;
+	struct iovec *tap_iov;
 	unsigned int i;
 
 	if (events == EPOLLERR)
@@ -847,34 +848,29 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
 	}
 
 	if (ref.r.p.udp.udp.v6) {
-		n = recvmmsg(ref.r.s, udp6_l2_mh_sock, UDP_TAP_FRAMES, 0, NULL);
-		if (n <= 0)
-			return;
-
-		udp6_l2_mh_tap[0].msg_hdr.msg_iov = &udp6_l2_iov_tap[0];
-
-		for (i = 0; i < (unsigned)n; i++) {
-			udp_sock_fill_data_v6(c, i, ref,
-					      &msg_i, &msg_bufs, &msg_len, now);
-		}
-
-		udp6_l2_mh_tap[msg_i].msg_hdr.msg_iovlen = msg_bufs;
 		tap_mmh = udp6_l2_mh_tap;
+		sock_mmh = udp6_l2_mh_sock;
+		tap_iov = udp6_l2_iov_tap;
 	} else {
-		n = recvmmsg(ref.r.s, udp4_l2_mh_sock, UDP_TAP_FRAMES, 0, NULL);
-		if (n <= 0)
-			return;
+		tap_mmh = udp4_l2_mh_tap;
+		sock_mmh = udp4_l2_mh_sock;
+		tap_iov = udp4_l2_iov_tap;
+	}
 
-		udp4_l2_mh_tap[0].msg_hdr.msg_iov = &udp4_l2_iov_tap[0];
+	n = recvmmsg(ref.r.s, sock_mmh, UDP_TAP_FRAMES, 0, NULL);
+	if (n <= 0)
+		return;
 
-		for (i = 0; i < (unsigned)n; i++) {
+	tap_mmh[0].msg_hdr.msg_iov = &tap_iov[0];
+	for (i = 0; i < (unsigned)n; i++) {
+		if (ref.r.p.udp.udp.v6)
+			udp_sock_fill_data_v6(c, i, ref,
+					      &msg_i, &msg_bufs, &msg_len, now);
+		else
 			udp_sock_fill_data_v4(c, i, ref,
 					      &msg_i, &msg_bufs, &msg_len, now);
-		}
-
-		udp4_l2_mh_tap[msg_i].msg_hdr.msg_iovlen = msg_bufs;
-		tap_mmh = udp4_l2_mh_tap;
 	}
+	tap_mmh[msg_i].msg_hdr.msg_iovlen = msg_bufs;
 
 	if (c->mode == MODE_PASTA)
 		return;
-- 
2.38.1