Merge branch 'net-add-sockaddr_inet-unified-address-structure'

Kees Cook says:

====================
net: Add sockaddr_inet unified address structure

Repeating patch 1, as it has the rationale:

    There are cases in networking (e.g. wireguard, sctp) where a union is
    used to provide coverage for either IPv4 or IPv6 network addresses,
    and they include an embedded "struct sockaddr" as well (for "sa_family"
    and raw "sa_data" access). The current struct sockaddr contains a
    flexible array, which means these unions should not be further embedded
    in other structs because they do not technically have a fixed size (and
    are generating warnings for the coming -Wflexible-array-not-at-end flag
    addition). But the future changes to make struct sockaddr a fixed size
    (i.e. with a 14 byte sa_data member) make the "sa_data" uses with an IPv6
    address a potential place for the compiler to get upset about object size
    mismatches. Therefore, we need a sockaddr that cleanly provides both an
    sa_family member and an appropriately fixed-sized sa_data member that does
    not bloat member usage via the potential alternative of sockaddr_storage
    to cover both IPv4 and IPv6, to avoid unseemly churn in the affected code
    bases.

    Introduce sockaddr_inet as a unified structure for holding both IPv4 and
    IPv6 addresses (i.e. large enough to accommodate sockaddr_in6).

    The structure is defined in linux/in6.h since its max size is sized
    based on sockaddr_in6 and provides a more specific alternative to the
    generic sockaddr_storage for IPv4 with IPv6 address family handling.

    The "sa_family" member doesn't use the sa_family_t type to avoid needing
    layer violating header inclusions.

Also includes the replacements for wireguard and sctp.
====================

Link: https://patch.msgid.link/20250722171528.work.209-kees@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

drivers/net/wireguard/peer.h

@@ -20,7 +20,7 @@ struct wg_device;
 
 struct endpoint {
 	union {
-		struct sockaddr addr;
+		struct sockaddr_inet addr;     /* Large enough for both address families */
 		struct sockaddr_in addr4;
 		struct sockaddr_in6 addr6;
 	};

include/linux/in6.h

@@ -18,6 +18,13 @@
 
 #include <uapi/linux/in6.h>
 
+/* Large enough to hold both sockaddr_in and sockaddr_in6. */
+struct sockaddr_inet {
+	unsigned short	sa_family;
+	char		sa_data[sizeof(struct sockaddr_in6) -
+				sizeof(unsigned short)];
+};
+
 /* IPv6 Wildcard Address (::) and Loopback Address (::1) defined in RFC2553
  * NOTE: Be aware the IN6ADDR_* constants and in6addr_* externals are defined
  * in network byte order, not in host byte order as are the IPv4 equivalents

include/net/sctp/structs.h

@@ -51,9 +51,9 @@
  * We should wean ourselves off this.
  */
 union sctp_addr {
+	struct sockaddr_inet sa;	/* Large enough for both address families */
 	struct sockaddr_in v4;
 	struct sockaddr_in6 v6;
-	struct sockaddr sa;
 };
 
 /* Forward declarations for data structures. */