mnl: fix --echo buffer size again

If restart is triggered with --echo, it causes rules to be duplicated
which is not correct. Remove restart logic.

1. If user passes --echo, use a default 4mb buffer.
2. assume each element in the batch will result in a 1k
   notification.

This passes tests both in x86_64 and s390.

Joint work with Florian Westphal.

Fixes: 877baf9538f6 ("src: mnl: retry when we hit -ENOBUFS")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 14 insertions, 12 deletions

diff --git a/src/mnl.c b/src/mnl.c
index 9c1f5356..8031bd6a 100644
--- a/src/mnl.c
+++ b/src/mnl.c
@@ -304,6 +304,8 @@ static ssize_t mnl_nft_socket_sendmsg(struct netlink_ctx *ctx,
 	return sendmsg(mnl_socket_get_fd(ctx->nft->nf_sock), msg, 0);
 }
 
+#define NFT_MNL_ECHO_RCVBUFF_DEFAULT	(MNL_SOCKET_BUFFER_SIZE * 1024)
+
 int mnl_batch_talk(struct netlink_ctx *ctx, struct list_head *err_list,
 		   uint32_t num_cmds)
 {
@@ -311,8 +313,6 @@ int mnl_batch_talk(struct netlink_ctx *ctx, struct list_head *err_list,
 	int ret, fd = mnl_socket_get_fd(nl), portid = mnl_socket_get_portid(nl);
 	uint32_t iov_len = nftnl_batch_iovec_len(ctx->batch);
 	char rcv_buf[MNL_SOCKET_BUFFER_SIZE];
-	unsigned int enobuf_restarts = 0;
-	size_t avg_msg_size, batch_size;
 	const struct sockaddr_nl snl = {
 		.nl_family = AF_NETLINK
 	};
@@ -321,17 +321,24 @@ int mnl_batch_talk(struct netlink_ctx *ctx, struct list_head *err_list,
 		.tv_usec	= 0
 	};
 	struct iovec iov[iov_len];
-	unsigned int scale = 4;
 	struct msghdr msg = {};
+	unsigned int rcvbufsiz;
+	size_t batch_size;
 	fd_set readfds;
 
 	mnl_set_sndbuffer(ctx->nft->nf_sock, ctx->batch);
 
 	batch_size = mnl_nft_batch_to_msg(ctx, &msg, &snl, iov, iov_len);
-	avg_msg_size = div_round_up(batch_size, num_cmds);
 
-restart:
-	mnl_set_rcvbuffer(ctx->nft->nf_sock, num_cmds * avg_msg_size * scale);
+	if (nft_output_echo(&ctx->nft->output)) {
+		rcvbufsiz = num_cmds * 1024;
+		if (rcvbufsiz < NFT_MNL_ECHO_RCVBUFF_DEFAULT)
+			rcvbufsiz = NFT_MNL_ECHO_RCVBUFF_DEFAULT;
+	} else {
+		rcvbufsiz = num_cmds * div_round_up(batch_size, num_cmds) * 4;
+	}
+
+	mnl_set_rcvbuffer(ctx->nft->nf_sock, rcvbufsiz);
 
 	ret = mnl_nft_socket_sendmsg(ctx, &msg);
 	if (ret == -1)
@@ -350,13 +357,8 @@ restart:
 			break;
 
 		ret = mnl_socket_recvfrom(nl, rcv_buf, sizeof(rcv_buf));
-		if (ret == -1) {
-			if (errno == ENOBUFS && enobuf_restarts++ < 3) {
-				scale *= 2;
-				goto restart;
-			}
+		if (ret == -1)
 			return -1;
-		}
 
 		ret = mnl_cb_run(rcv_buf, ret, 0, portid, &netlink_echo_callback, ctx);
 		/* Continue on error, make sure we get all acknowledgments */