trafgen: fix packet socket initialization with multiple CPUs

The commit 78c13b71e196 ("trafgen: Allow to generate packets
to output pcap file") introduced a regression when output is
a network device and multiple CPU are in use: the packet
socket is created before fork() and thus the socket is shared
among all the processes: all of them except the first will
fail while setting the tx_ring.

Fix it splitting the io open() helper in a create() op,
called before forking, and the open() op called by each process.

Fixes: 78c13b71e196 ("trafgen: Allow to generate packets to output pcap file")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

3 files changed, 20 insertions, 11 deletions

diff --git a/trafgen.c b/trafgen.c
index 9b54399..9c5a9a6 100644
--- a/trafgen.c
+++ b/trafgen.c
@@ -977,6 +977,7 @@ static void main_loop(struct ctx *ctx, char *confname, bool slow,
 		fflush(stdout);
 	}
 
+	dev_io_open(ctx->dev_out);
 	if (dev_io_is_netdev(ctx->dev_out) && ctx->qdisc_path == false)
 		set_sock_qdisc_bypass(dev_io_fd_get(ctx->dev_out), ctx->verbose);
 
@@ -1266,12 +1267,13 @@ int main(int argc, char **argv)
 	xlockme();
 
 	if (ctx.pcap_in) {
-		ctx.dev_in = dev_io_open(ctx.pcap_in, DEV_IO_IN);
+		ctx.dev_in = dev_io_create(ctx.pcap_in, DEV_IO_IN);
 		if (!ctx.dev_in)
 			panic("Failed to open input device\n");
+		dev_io_open(ctx.dev_in);
 	}
 
-	ctx.dev_out = dev_io_open(ctx.device, DEV_IO_OUT);
+	ctx.dev_out = dev_io_create(ctx.device, DEV_IO_OUT);
 	if (!ctx.dev_out)
 		panic("Failed to open output device\n");
 
diff --git a/trafgen_dev.c b/trafgen_dev.c
index f65442f..489da98 100644
--- a/trafgen_dev.c
+++ b/trafgen_dev.c
@@ -242,10 +242,11 @@ static const struct dev_io_ops dev_cfg_ops = {
 	.close = dev_cfg_close,
 };
 
-struct dev_io *dev_io_open(const char *name, enum dev_io_mode_t mode)
+struct dev_io *dev_io_create(const char *name, enum dev_io_mode_t mode)
 {
 	struct dev_io *dev = xzmalloc(sizeof(struct dev_io));
 
+	dev->mode = mode;
 	if (strstr(name, ".pcap")) {
 		dev->name = xstrdup(name);
 		dev->ops = &dev_pcap_ops;
@@ -260,16 +261,20 @@ struct dev_io *dev_io_open(const char *name, enum dev_io_mode_t mode)
 		return NULL;
 	}
 
-	if (dev->ops->open) {
-		if (dev->ops->open(dev, name, mode)) {
-			xfree(dev);
-			return NULL;
-		}
-	}
-
 	return dev;
 };
 
+extern void dev_io_open(struct dev_io *dev)
+{
+	bug_on(!dev);
+	bug_on(!dev->ops);
+
+	if (dev->ops->open)
+		if (dev->ops->open(dev, dev->name, dev->mode))
+			panic("Cannot open io %s mode %d\n", dev->name,
+			      dev->mode);
+}
+
 int dev_io_write(struct dev_io *dev, struct packet *pkt)
 {
 	bug_on(!dev);
diff --git a/trafgen_dev.h b/trafgen_dev.h
index 80086d7..bcb88f3 100644
--- a/trafgen_dev.h
+++ b/trafgen_dev.h
@@ -24,6 +24,7 @@ struct dev_io {
 	uint32_t pcap_magic;
 	bool is_initialized;
 	enum pcap_mode pcap_mode;
+	enum dev_io_mode_t mode;
 	size_t buf_len;
 	uint8_t *buf;
 
@@ -39,7 +40,8 @@ struct dev_io_ops {
 	void(*close) (struct dev_io *dev);
 };
 
-extern struct dev_io *dev_io_open(const char *name, enum dev_io_mode_t mode);
+extern struct dev_io *dev_io_create(const char *name, enum dev_io_mode_t mode);
+extern void dev_io_open(struct dev_io *dev);
 extern int dev_io_write(struct dev_io *dev, struct packet *pkt);
 extern struct packet *dev_io_read(struct dev_io *dev);
 extern int dev_io_ifindex_get(struct dev_io *dev);