On Mon, Nov 07, 2022 at 07:08:19PM +0100, Stefano Brivio wrote:On Fri, 4 Nov 2022 19:43:25 +1100 David Gibson <david(a)gibson.dropbear.id.au> wrote:Yeah, we could. Originally I was trying to make this even more hidden, with the decode function returning a struct in_addr *, that would be NULL if the IPv6 address wasn't v4-mapped. Unfortunately I seemed to hit more weird compiler aliasing issues that caused hard to predict failures. Hrm... your comment gives me some thoughts on maybe a better way to do this, I'll look into it.In the tcp_conn structure we have space for an IPv6 address, and use IPv4-mapped IPv6 addresses to describe IPv4 connections. We open code the construction of those IPv4-mapped address in two places. Avoid the duplication with a helper function.Much nicer, indeed.Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- tcp.c | 9 ++------- util.c | 20 ++++++++++++++++++++ util.h | 1 + 3 files changed, 23 insertions(+), 7 deletions(-) diff --git a/tcp.c b/tcp.c index 3d48d6e..26dd268 100644 --- a/tcp.c +++ b/tcp.c @@ -2217,9 +2217,7 @@ static void tcp_conn_from_tap(struct ctx *c, int af, const void *addr, sa = (struct sockaddr *)&addr4; sl = sizeof(addr4); - memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero)); - memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one)); - memcpy(&conn->a.a4.a, addr, sizeof(conn->a.a4.a)); + encode_ip4mapped_ip6(&conn->a.a6, addr); } else { sa = (struct sockaddr *)&addr6; sl = sizeof(addr6); @@ -2902,15 +2900,12 @@ static void tcp_conn_from_sock(struct ctx *c, union epoll_ref ref, memcpy(&sa4, &sa, sizeof(sa4)); - memset(&conn->a.a4.zero, 0, sizeof(conn->a.a4.zero)); - memset(&conn->a.a4.one, 0xff, sizeof(conn->a.a4.one)); - if (IN4_IS_ADDR_LOOPBACK(&sa4.sin_addr) || IN4_IS_ADDR_UNSPECIFIED(&sa4.sin_addr) || IN4_ARE_ADDR_EQUAL(&sa4.sin_addr, &c->ip4.addr_seen)) sa4.sin_addr = c->ip4.gw; - conn->a.a4.a = sa4.sin_addr; + encode_ip4mapped_ip6(&conn->a.a6, &sa4.sin_addr); conn->sock_port = ntohs(sa4.sin_port); conn->tap_port = ref.r.p.tcp.tcp.index; diff --git a/util.c b/util.c index 514bd44..257d0b6 100644 --- a/util.c +++ b/util.c @@ -482,3 +482,23 @@ int write_file(const char *path, const char *buf) close(fd); return len == 0 ? 0 : -1; } + +struct ip4mapped_ip6 { + uint8_t zero[10]; + uint8_t one[2]; + struct in_addr a4; +};Document fields even if they're obvious. Can we reuse this part in struct conn instead of using struct in6_addr there as you do later in 7/10? I don't have a strong preference though.-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson+ +/** + * encode_ip4mapped_ip6() - Convert an IPv4 address to an IPv4-mapped IPv6 address + * @ip6: Buffer to store the IPv4-mapped IPv6 address + * @ip4: IPv4 address, network order + */ +void encode_ip4mapped_ip6(struct in6_addr *ip6, const void *ip4) +{ + struct ip4mapped_ip6 *a = (struct ip4mapped_ip6 *)ip6; + + memset(&a->zero, 0, sizeof(a->zero)); + memset(&a->one, 0xff, sizeof(a->one)); + memcpy(&a->a4, ip4, sizeof(a->a4)); +} diff --git a/util.h b/util.h index 2d4e1ff..f7d6a6f 100644 --- a/util.h +++ b/util.h @@ -209,5 +209,6 @@ void write_pidfile(int fd, pid_t pid); int __daemon(int pidfile_fd, int devnull_fd); int fls(unsigned long x); int write_file(const char *path, const char *buf); +void encode_ip4mapped_ip6(struct in6_addr *ip6, const void *ip4); #endif /* UTIL_H */