ring: prepare setup_rx_ring_layout for support in v2/v3

Prepare setup_rx_ring_layout for both, v2 and v3. Also do some checks
during compile time if offsets stay the same as we operate on different
union mappings.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

6 files changed, 28 insertions, 11 deletions

diff --git a/built_in.h b/built_in.h
index fa2f0c8..ea81257 100644
--- a/built_in.h
+++ b/built_in.h
@@ -153,6 +153,10 @@ typedef uint8_t		u8;
 # define build_bug_on_zero(e)	(sizeof(char[1 - 2 * !!(e)]) - 1)
 #endif
 
+#ifndef build_bug_on
+# define build_bug_on(e)	((void)sizeof(char[1 - 2*!!(e)]))
+#endif
+
 #ifndef bug_on
 # define bug_on(cond)		assert(!(cond))
 #endif
diff --git a/netsniff-ng.c b/netsniff-ng.c
index 7070873..76fafed 100644
--- a/netsniff-ng.c
+++ b/netsniff-ng.c
@@ -372,7 +372,7 @@ static void receive_to_xmit(struct ctx *ctx)
 		bpf_dump_all(&bpf_ops);
 	bpf_attach_to_sock(rx_sock, &bpf_ops);
 
-	setup_rx_ring_layout(rx_sock, &rx_ring, size_in, ctx->jumbo);
+	setup_rx_ring_layout(rx_sock, &rx_ring, size_in, ctx->jumbo, false);
 	create_rx_ring(rx_sock, &rx_ring, ctx->verbose);
 	mmap_rx_ring(rx_sock, &rx_ring);
 	alloc_rx_ring_frames(&rx_ring);
@@ -851,7 +851,7 @@ static void recv_only_or_dump(struct ctx *ctx)
 
 	set_sockopt_hwtimestamp(sock, ctx->device_in);
 
-	setup_rx_ring_layout(sock, &rx_ring, size, ctx->jumbo);
+	setup_rx_ring_layout(sock, &rx_ring, size, ctx->jumbo, false);
 	create_rx_ring(sock, &rx_ring, ctx->verbose);
 	mmap_rx_ring(sock, &rx_ring);
 	alloc_rx_ring_frames(&rx_ring);
diff --git a/ring.h b/ring.h
index 5e47d37..f618a35 100644
--- a/ring.h
+++ b/ring.h
@@ -82,6 +82,13 @@ static inline unsigned int ring_frame_size(struct ring *ring)
 	return ring->layout.tp_frame_size;
 }
 
+static inline void ring_verify_layout(struct ring *ring)
+{
+	bug_on(ring->layout.tp_block_size  < ring->layout.tp_frame_size);
+	bug_on((ring->layout.tp_block_size % ring->layout.tp_frame_size) != 0);
+	bug_on((ring->layout.tp_block_size % getpagesize()) != 0);
+}
+
 static inline void tpacket_hdr_clone(struct tpacket2_hdr *thdrd,
 				     struct tpacket2_hdr *thdrs)
 {
diff --git a/ring_rx.c b/ring_rx.c
index 27c87d3..12ce086 100644
--- a/ring_rx.c
+++ b/ring_rx.c
@@ -36,7 +36,7 @@ void destroy_rx_ring(int sock, struct ring *ring)
 }
 
 void setup_rx_ring_layout(int sock, struct ring *ring, unsigned int size,
-			  int jumbo_support)
+			  int jumbo_support, bool v3)
 {
 	fmemset(&ring->layout, 0, sizeof(ring->layout));
 
@@ -50,17 +50,25 @@ void setup_rx_ring_layout(int sock, struct ring *ring, unsigned int size,
 	ring->layout.tp_frame_nr = ring->layout.tp_block_size /
 				   ring->layout.tp_frame_size *
 				   ring->layout.tp_block_nr;
+	if (v3) {
+		/* Pass out, if this will ever change and we do crap on it! */
+		build_bug_on(offsetof(struct tpacket_req, tp_frame_nr) !=
+			     offsetof(struct tpacket_req3, tp_frame_nr) &&
+			     sizeof(struct tpacket_req) !=
+			     offsetof(struct tpacket_req3, tp_retire_blk_tov));
+
+		set_sockopt_tpacket_v3(sock);
+	} else {
+		set_sockopt_tpacket_v2(sock);
+	}
 
-	bug_on(ring->layout.tp_block_size < ring->layout.tp_frame_size);
-	bug_on((ring->layout.tp_block_size % ring->layout.tp_frame_size) != 0);
-	bug_on((ring->layout.tp_block_size % getpagesize()) != 0);
+	ring_verify_layout(ring);
 }
 
 void create_rx_ring(int sock, struct ring *ring, int verbose)
 {
 	int ret;
 
-	set_sockopt_tpacket_v2(sock);
 retry:
 	ret = setsockopt(sock, SOL_PACKET, PACKET_RX_RING, &ring->layout,
 			 sizeof(ring->layout));
diff --git a/ring_rx.h b/ring_rx.h
index 0e0478c..8556e3a 100644
--- a/ring_rx.h
+++ b/ring_rx.h
@@ -16,7 +16,7 @@ extern void mmap_rx_ring(int sock, struct ring *ring);
 extern void alloc_rx_ring_frames(struct ring *ring);
 extern void bind_rx_ring(int sock, struct ring *ring, int ifindex);
 extern void setup_rx_ring_layout(int sock, struct ring *ring,
-				 unsigned int size, int jumbo_support);
+				 unsigned int size, int jumbo_support, bool v3);
 
 static inline int user_may_pull_from_rx(struct tpacket2_hdr *hdr)
 {
diff --git a/ring_tx.c b/ring_tx.c
index f91f7f7..b7cde7e 100644
--- a/ring_tx.c
+++ b/ring_tx.c
@@ -61,9 +61,7 @@ void setup_tx_ring_layout(int sock, struct ring *ring, unsigned int size,
 				   ring->layout.tp_frame_size *
 				   ring->layout.tp_block_nr;
 
-	bug_on(ring->layout.tp_block_size < ring->layout.tp_frame_size);
-	bug_on((ring->layout.tp_block_size % ring->layout.tp_frame_size) != 0);
-	bug_on((ring->layout.tp_block_size % getpagesize()) != 0);
+	ring_verify_layout(ring);
 }
 
 void create_tx_ring(int sock, struct ring *ring, int verbose)