[PATCH v2] net: revert add IPv6 traffic class and flow label fields
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REVIEWED: 1 (1M)
From: Morten Brørup <hidden>
Date: 2026-09-29 07:36:22
Subsystem:
library code, the rest · Maintainers:
Andrew Morton, Linus Torvalds
1 review trailer.
The IPv6 header bitfields "version", "ds", "ecn", and "flow_label"
are not organized correctly on little endian architectures.
On little endian, a 32-bit bitfield is allocated from the least
significant bit of the host order word, but "vtc_flow" is stored in
network order. All four fields therefore read and write the wrong
bits. For example, setting "version" to 6 writes 0x60 into the last
byte of the word.
"ds" and "flow_label" are not contiguous in memory on little endian,
so no reordering of bitfields can express them.
Reverted the patch introducing these bitfields.
PS: There is a GCC attribute to fix this, but nothing similar is
offered by Clang or MSVC:
__attribute__((scalar_storage_order("big-endian")))
Bugzilla ID: 1679
Fixes: cba27998dc81 ("net: add IPv6 traffic class and flow label fields")
Cc: stable@dpdk.org
Reported-by: Maxime Leroy <redacted>
Signed-off-by: Morten Brørup <redacted>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
---
v2: Updated commit message and release notes. (AI advanced model)
---
doc/guides/rel_notes/release_26_11.rst | 5 +++++
lib/net/rte_ip6.h | 18 +-----------------
2 files changed, 6 insertions(+), 17 deletions(-)
diff --git a/doc/guides/rel_notes/release_26_11.rst b/doc/guides/rel_notes/release_26_11.rst
index 4b3e5d995c..52ccc8f787 100644
--- a/doc/guides/rel_notes/release_26_11.rst
+++ b/doc/guides/rel_notes/release_26_11.rst@@ -79,6 +79,11 @@ Removed Items ``rte_rib6_is_equal`` * table: ``RTE_LPM_IPV6_ADDR_SIZE`` + * net: Removed ``version``, ``ds``, ``ecn`` and ``flow_label`` + bitfields from ``struct rte_ipv6_hdr``. They accessed the wrong + bits on little endian. Use ``vtc_flow`` with the + ``RTE_IPV6_HDR_*_MASK`` and ``RTE_IPV6_HDR_*_SHIFT`` macros. + API Changes -----------
diff --git a/lib/net/rte_ip6.h b/lib/net/rte_ip6.h
index d1abf1f5d5..25be328955 100644
--- a/lib/net/rte_ip6.h
+++ b/lib/net/rte_ip6.h@@ -467,23 +467,7 @@ rte_ether_mcast_from_ipv6(struct rte_ether_addr *mac, const struct rte_ipv6_addr * IPv6 Header */ struct __rte_aligned(2) __rte_packed_begin rte_ipv6_hdr { - union { - rte_be32_t vtc_flow; /**< IP version, traffic class & flow label. */ - __extension__ - struct { -#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN - uint32_t flow_label:20; /**< Flow label */ - uint32_t ecn:2; /**< ECN */ - uint32_t ds:6; /**< Differentiated services */ - uint32_t version:4; /**< Version */ -#elif RTE_BYTE_ORDER == RTE_BIG_ENDIAN - uint32_t version:4; /**< Version */ - uint32_t ds:6; /**< Differentiated services */ - uint32_t ecn:2; /**< ECN */ - uint32_t flow_label:20; /**< Flow label */ -#endif - }; - }; + rte_be32_t vtc_flow; /**< IP version, traffic class & flow label. */ rte_be16_t payload_len; /**< IP payload size, including ext. headers */ uint8_t proto; /**< Protocol, next header. */ uint8_t hop_limits; /**< Hop limits. */
--
2.43.0