net: Add sockaddr_inet unified address structure

Hi!

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.

Thanks,

-Kees

Kees Cook (3):
ipv6: Add sockaddr_inet unified address structure
wireguard: peer: Replace sockaddr with sockaddr_inet
sctp: Replace sockaddr with sockaddr_inet in sctp_addr union

 drivers/net/wireguard/peer.h | 2 +-
 include/linux/in6.h          | 7 +++++++
 include/net/sctp/structs.h   | 2 +-
 3 files changed, 9 insertions(+), 2 deletions(-)

2.34.1

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.

---
 include/linux/in6.h | 7 +++++++
 1 file changed, 7 insertions(+)

index 0777a21cbf86..403f926d33d8 100644
@@ -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

2.34.1

As part of the removal of the variably-sized sockaddr for kernel internals, replace struct sockaddr with sockaddr_inet in the endpoint union.

No binary changes; the union size remains unchanged due to sockaddr_inet matching the size of sockaddr_in6.

---
Cc: "Jason A. Donenfeld" <[email protected]>
Cc: Andrew Lunn <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>

---
 drivers/net/wireguard/peer.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 76e4d3128ad4..718fb42bdac7 100644
@@ -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;
 	};

2.34.1

As part of the removal of the variably-sized sockaddr for kernel internals, replace struct sockaddr with sockaddr_inet in the sctp_addr union.

No binary changes; the union size remains unchanged due to sockaddr_inet matching the size of sockaddr_in6.

---
Cc: Marcelo Ricardo Leitner <[email protected]>
Cc: Xin Long <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: Simon Horman <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>

---
 include/net/sctp/structs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 1ad7ce71d0a7..8a540ad9b509 100644
@@ -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. */

2.34.1

+ Iwashima-san and Willem

This series looks like something you should review