[dpdk-dev] [PATCH v4 5/8] net/ether: mark ethernet addresses as being 2-byte aligned

Stephen Hemminger stephen at networkplumber.org
Wed Jun 5 20:09:45 CEST 2019


From: Bruce Richardson <bruce.richardson at intel.com>

When including the rte_ether.h header in applications with warnings
enabled, a warning was given because of the assumption of 2-byte alignment
of ethernet addresses when processing them.

.../include/rte_ether.h:149:2: warning: converting a packed ‘const
  struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
  {aka ‘const short unsigned int’} pointer (alignment 2) may result in
  an unaligned pointer value [-Waddress-of-packed-member]
149 |  const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
    |  ^~~~~

Since ethernet addresses should always be aligned on a two-byte boundary,
we can just inform the compiler of this assumption to remove the warnings
and allow us to always access the addresses using 16-bit operations.

Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
Reviewed-by: Andrew Rybchenko <arybchenko at solarflare.com>
---
 lib/librte_net/rte_ether.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
index feb35a33c94b..d7b76ddf63eb 100644
--- a/lib/librte_net/rte_ether.h
+++ b/lib/librte_net/rte_ether.h
@@ -58,7 +58,8 @@ extern "C" {
  * See http://standards.ieee.org/regauth/groupmac/tutorial.html
  */
 struct rte_ether_addr {
-	uint8_t addr_bytes[RTE_ETHER_ADDR_LEN]; /**< Addr bytes in tx order */
+	uint8_t addr_bytes[RTE_ETHER_ADDR_LEN] __rte_aligned(2);
+	/**< Addr bytes in tx order */
 } __attribute__((__packed__));
 
 #define RTE_ETHER_LOCAL_ADMIN_ADDR 0x02 /**< Locally assigned Eth. address. */
@@ -81,8 +82,8 @@ struct rte_ether_addr {
 static inline int rte_is_same_ether_addr(const struct rte_ether_addr *ea1,
 				     const struct rte_ether_addr *ea2)
 {
-	const unaligned_uint16_t *w1 = (const uint16_t *)ea1;
-	const unaligned_uint16_t *w2 = (const uint16_t *)ea2;
+	const uint16_t *w1 = (const uint16_t *)ea1;
+	const uint16_t *w2 = (const uint16_t *)ea2;
 
 	return ((w1[0] ^ w2[0]) | (w1[1] ^ w2[1]) | (w1[2] ^ w2[2])) == 0;
 }
@@ -99,7 +100,7 @@ static inline int rte_is_same_ether_addr(const struct rte_ether_addr *ea1,
  */
 static inline int rte_is_zero_ether_addr(const struct rte_ether_addr *ea)
 {
-	const unaligned_uint16_t *w = (const uint16_t *)ea;
+	const uint16_t *w = (const uint16_t *)ea;
 
 	return (w[0] | w[1] | w[2]) == 0;
 }
@@ -146,7 +147,7 @@ static inline int rte_is_multicast_ether_addr(const struct rte_ether_addr *ea)
  */
 static inline int rte_is_broadcast_ether_addr(const struct rte_ether_addr *ea)
 {
-	const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
+	const uint16_t *ea_words = (const uint16_t *)ea;
 
 	return (ea_words[0] == 0xFFFF && ea_words[1] == 0xFFFF &&
 		ea_words[2] == 0xFFFF);
-- 
2.20.1



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