[PATCH 14/16] inany: Introduce union sockaddr_inany

[David Gibson <david@gibson.dropbear.id.au>]

There are a number of places where we want to handle either a sockaddr_in
or a sockaddr_in6.  In some of those we use a void *, which works ok and
matches some standard library interfaces, but doesn't give a signature
level hint that we're dealing with only sockaddr_in or sockaddr_in6, not
(say) sockaddr_un or another type of socket address.  Other places we use a
sockaddr_storage, which also works, but has the same problem in addition to
allocating more on the stack than we need to.

Introduce union sockaddr_inany to explictly handle this case: it has
variants for sockaddr_in and sockaddr_in6.  Use it in a number of
places where it's easy to do so.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 icmp.c       | 18 ++++++------------
 inany.h      | 33 +++++++++++++++++++++------------
 tcp.c        | 11 +++++------
 tcp_splice.c |  2 +-
 tcp_splice.h |  3 ++-
 5 files changed, 35 insertions(+), 32 deletions(-)

diff --git a/icmp.c b/icmp.c
index faa38c81..fb2fcafc 100644
--- a/icmp.c
+++ b/icmp.c
@@ -36,6 +36,8 @@
 #include "passt.h"
 #include "tap.h"
 #include "log.h"
+#include "siphash.h"
+#include "inany.h"
 #include "icmp.h"
 
 #define ICMP_ECHO_TIMEOUT	60 /* s, timeout for ICMP socket activity */
@@ -67,13 +69,9 @@ void icmp_sock_handler(const struct ctx *c, sa_family_t af, union epoll_ref ref)
 	struct icmp_id_sock *const id_sock = af == AF_INET
 		? &icmp_id_map[V4][ref.icmp.id] : &icmp_id_map[V6][ref.icmp.id];
 	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
-	char buf[USHRT_MAX];
-	union {
-		struct sockaddr sa;
-		struct sockaddr_in sa4;
-		struct sockaddr_in6 sa6;
-	} sr;
+	union sockaddr_inany sr;
 	socklen_t sl = sizeof(sr);
+	char buf[USHRT_MAX];
 	uint16_t seq;
 	ssize_t n;
 
@@ -86,7 +84,7 @@ void icmp_sock_handler(const struct ctx *c, sa_family_t af, union epoll_ref ref)
 		     pname, strerror(errno));
 		return;
 	}
-	if (sr.sa.sa_family != af)
+	if (sr.sa_family != af)
 		goto unexpected;
 
 	if (af == AF_INET) {
@@ -214,11 +212,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af,
 		     const struct pool *p, const struct timespec *now)
 {
 	const char *const pname = af == AF_INET ? "ICMP" : "ICMPv6";
-	union {
-		struct sockaddr sa;
-		struct sockaddr_in sa4;
-		struct sockaddr_in6 sa6;
-	} sa = { .sa.sa_family = af };
+	union sockaddr_inany sa = { .sa_family = af };
 	const socklen_t sl = af == AF_INET ? sizeof(sa.sa4) : sizeof(sa.sa6);
 	struct icmp_id_sock *id_sock;
 	uint16_t id, seq;
diff --git a/inany.h b/inany.h
index d08d1f33..474e09d0 100644
--- a/inany.h
+++ b/inany.h
@@ -9,6 +9,8 @@
 #ifndef INANY_H
 #define INANY_H
 
+struct siphash_state;
+
 /** union inany_addr - Represents either an IPv4 or IPv6 address
  * @a6:			Address as an IPv6 address, may be IPv4-mapped
  * @v4mapped.zero:	All zero-bits for an IPv4 address
@@ -32,6 +34,19 @@ static_assert(sizeof(union inany_addr) == sizeof(struct in6_addr),
 static_assert(_Alignof(union inany_addr) == _Alignof(uint32_t),
 	      "union inany_addr has unexpected alignment");
 
+/** union sockaddr_inany - Either a sockaddr_in or a sockaddr_in6
+ * @sa_family:	Address family, AF_INET or AF_INET6
+ * @sa:		Plain struct sockaddr (useful to avoid casts)
+ * @sa4:	IPv4 socket address, valid if sa_family == AF_INET
+ * @sa6:	IPv6 socket address, valid if sa_family == AF_INET6
+ */
+union sockaddr_inany {
+	sa_family_t		sa_family;
+	struct sockaddr		sa;
+	struct sockaddr_in	sa4;
+	struct sockaddr_in6	sa6;
+};
+
 /** inany_v4 - Extract IPv4 address, if present, from IPv[46] address
  * @addr:	IPv4 or IPv6 address
  *
@@ -91,23 +106,17 @@ static inline void inany_from_af(union inany_addr *aa,
 /** inany_from_sockaddr - Extract IPv[46] address and port number from sockaddr
  * @aa:		Pointer to store IPv[46] address
  * @port:	Pointer to store port number, host order
- * @addr:	struct sockaddr_in (IPv4) or struct sockaddr_in6 (IPv6)
+ * @addr:	AF_INET or AF_INET6 socket address
  */
 static inline void inany_from_sockaddr(union inany_addr *aa, in_port_t *port,
-				       const void *addr)
+				       const union sockaddr_inany *sa)
 {
-	const struct sockaddr *sa = (const struct sockaddr *)addr;
-
 	if (sa->sa_family == AF_INET6) {
-		struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)sa;
-
-		inany_from_af(aa, AF_INET6, &sa6->sin6_addr);
-		*port = ntohs(sa6->sin6_port);
+		inany_from_af(aa, AF_INET6, &sa->sa6.sin6_addr);
+		*port = ntohs(sa->sa6.sin6_port);
 	} else if (sa->sa_family == AF_INET) {
-		struct sockaddr_in *sa4 = (struct sockaddr_in *)sa;
-
-		inany_from_af(aa, AF_INET, &sa4->sin_addr);
-		*port = ntohs(sa4->sin_port);
+		inany_from_af(aa, AF_INET, &sa->sa4.sin_addr);
+		*port = ntohs(sa->sa4.sin_port);
 	} else {
 		/* Not valid to call with other address families */
 		ASSERT(0);
diff --git a/tcp.c b/tcp.c
index bb914bff..a52a1f84 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2685,7 +2685,7 @@ static void tcp_snat_inbound(const struct ctx *c, union inany_addr *addr)
 static void tcp_tap_conn_from_sock(struct ctx *c,
 				   union tcp_listen_epoll_ref ref,
 				   struct tcp_tap_conn *conn, int s,
-				   const struct sockaddr *sa,
+				   const union sockaddr_inany *sa,
 				   const struct timespec *now)
 {
 	conn->f.type = FLOW_TCP;
@@ -2721,7 +2721,7 @@ static void tcp_tap_conn_from_sock(struct ctx *c,
 void tcp_listen_handler(struct ctx *c, union epoll_ref ref,
 			const struct timespec *now)
 {
-	struct sockaddr_storage sa;
+	union sockaddr_inany sa;
 	socklen_t sl = sizeof(sa);
 	union flow *flow;
 	int s;
@@ -2729,16 +2729,15 @@ void tcp_listen_handler(struct ctx *c, union epoll_ref ref,
 	if (c->no_tcp || !(flow = flow_alloc()))
 		return;
 
-	s = accept4(ref.fd, (struct sockaddr *)&sa, &sl, SOCK_NONBLOCK);
+	s = accept4(ref.fd, &sa.sa, &sl, SOCK_NONBLOCK);
 	if (s < 0)
 		goto cancel;
 
 	if (tcp_splice_conn_from_sock(c, ref.tcp_listen, &flow->tcp_splice,
-				      s, (struct sockaddr *)&sa))
+				      s, &sa))
 		return;
 
-	tcp_tap_conn_from_sock(c, ref.tcp_listen, &flow->tcp, s,
-			       (struct sockaddr *)&sa, now);
+	tcp_tap_conn_from_sock(c, ref.tcp_listen, &flow->tcp, s, &sa, now);
 	return;
 
 cancel:
diff --git a/tcp_splice.c b/tcp_splice.c
index 3b438313..3a2c0781 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -382,7 +382,7 @@ static int tcp_splice_connect(const struct ctx *c, struct tcp_splice_conn *conn,
 bool tcp_splice_conn_from_sock(const struct ctx *c,
 			       union tcp_listen_epoll_ref ref,
 			       struct tcp_splice_conn *conn, int s0,
-			       const struct sockaddr *sa)
+			       const union sockaddr_inany *sa)
 {
 	in_port_t srcport, dstport = ref.port;
 	union inany_addr src;
diff --git a/tcp_splice.h b/tcp_splice.h
index d3600807..f6557cd4 100644
--- a/tcp_splice.h
+++ b/tcp_splice.h
@@ -7,13 +7,14 @@
 #define TCP_SPLICE_H
 
 struct tcp_splice_conn;
+union sockaddr_inany;
 
 void tcp_splice_sock_handler(struct ctx *c, union epoll_ref ref,
 			     uint32_t events);
 bool tcp_splice_conn_from_sock(const struct ctx *c,
 			       union tcp_listen_epoll_ref ref,
 			       struct tcp_splice_conn *conn, int s0,
-			       const struct sockaddr *sa);
+			       const union sockaddr_inany *sa);
 void tcp_splice_init(struct ctx *c);
 
 #endif /* TCP_SPLICE_H */
-- 
@@ -7,13 +7,14 @@
 #define TCP_SPLICE_H
 
 struct tcp_splice_conn;
+union sockaddr_inany;
 
 void tcp_splice_sock_handler(struct ctx *c, union epoll_ref ref,
 			     uint32_t events);
 bool tcp_splice_conn_from_sock(const struct ctx *c,
 			       union tcp_listen_epoll_ref ref,
 			       struct tcp_splice_conn *conn, int s0,
-			       const struct sockaddr *sa);
+			       const union sockaddr_inany *sa);
 void tcp_splice_init(struct ctx *c);
 
 #endif /* TCP_SPLICE_H */
-- 
2.43.0