[PATCH v3 1/4] examples/server_node_efd: fix format overflow

[Stephen Hemminger <stephen@networkplumber.org>]

If format-truncation is enabled, the compiler detects a string overflow
since the snprintf() is putting ethernet address and new line
in buffer only sized for the address.

Since get_rx_queue_name() is used to create a ring name.
The buffer should be sized to be a valid ring name.
This fixes some format-overflow warnings and also corrects
for future errors.

In file included from ../examples/server_node_efd/efd_server/main.c:31:
In function ‘get_printable_mac_addr’,
    inlined from ‘do_stats_display’ at ../examples/server_node_efd/efd_server/main.c:136:3:
../lib/net/rte_ether.h:248:36: warning: ‘snprintf’ output truncated before the last format character [-Wformat-truncation=]
  248 | #define RTE_ETHER_ADDR_PRT_FMT     "%02X:%02X:%02X:%02X:%02X:%02X"
      |                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../examples/server_node_efd/efd_server/main.c:86:33: note: in expansion of macro ‘RTE_ETHER_ADDR_PRT_FMT’
   86 |                                 RTE_ETHER_ADDR_PRT_FMT "\n",
      |                                 ^~~~~~~~~~~~~~~~~~~~~~
../examples/server_node_efd/efd_server/main.c: In function ‘do_stats_display’:
../examples/server_node_efd/efd_server/main.c:86:59: note: format string is defined here
   86 |                                 RTE_ETHER_ADDR_PRT_FMT "\n",
      |

Fixes: 39aad0e88c58 ("examples/flow_distributor: new example to demonstrate EFD")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 examples/server_node_efd/efd_server/main.c | 2 +-
 examples/server_node_efd/shared/common.h   | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/examples/server_node_efd/efd_server/main.c b/examples/server_node_efd/efd_server/main.c
index 75ff0ea532..62c3f4a16d 100644
--- a/examples/server_node_efd/efd_server/main.c
+++ b/examples/server_node_efd/efd_server/main.c
@@ -68,7 +68,7 @@ static const char *
 get_printable_mac_addr(uint16_t port)
 {
 	static const char err_address[] = "00:00:00:00:00:00";
-	static char addresses[RTE_MAX_ETHPORTS][sizeof(err_address)];
+	static char addresses[RTE_MAX_ETHPORTS][RTE_ETHER_ADDR_FMT_SIZE + 1];
 	struct rte_ether_addr mac;
 	int ret;
 
diff --git a/examples/server_node_efd/shared/common.h b/examples/server_node_efd/shared/common.h
index e1ab7e62b7..6726e2031e 100644
--- a/examples/server_node_efd/shared/common.h
+++ b/examples/server_node_efd/shared/common.h
@@ -58,8 +58,9 @@ get_rx_queue_name(unsigned int id)
 	/*
 	 * Buffer for return value. Size calculated by %u being replaced
 	 * by maximum 3 digits (plus an extra byte for safety)
+	 * Used as ring name, so upper limit is ring name size.
 	 */
-	static char buffer[sizeof(MP_NODE_RXQ_NAME) + 2];
+	static char buffer[RTE_RING_NAMESIZE];
 
 	snprintf(buffer, sizeof(buffer), MP_NODE_RXQ_NAME, id);
 	return buffer;
-- 
2.51.0