On Thu, Nov 17, 2022 at 01:15:20AM +0100, Stefano Brivio wrote: > On Wed, 16 Nov 2022 15:42:07 +1100 > David Gibson wrote: > > > passt usually doesn't NAT, but it does do so for the remapping of the > > gateway address to refer to the host. Currently we perform this NAT with > > slightly different rules on both IPv4 addresses and IPv6 addresses, but not > > on IPv4-mapped IPv6 addresses. This means we won't correctly handle the > > case of an IPv4 connection over an IPv6 socket, which is possible on Linux > > (and probably other platforms). > > By the way, I really think it's just Linux, I can't think of other > examples. Hmm... so descriptions I've seen of the IPv4-mapped IPv6 addresses seem to imply this is the behaviour in a number of systems. e.g. https://en.wikipedia.org/wiki/IPv6#IPv4-mapped_IPv6_addresses > > Refactor tcp_conn_from_sock() to perform the NAT after converting either > > address family into an inany_addr, so IPv4 and and IPv4-mapped addresses > > have the same representation. > > > > With two new helpers this lets us remove the IPv4 and IPv6 specific paths > > from tcp_conn_from_sock(). > > > > Signed-off-by: David Gibson > > --- > > inany.h | 30 ++++++++++++++++++++++++++-- > > tcp.c | 62 ++++++++++++++++++++++++--------------------------------- > > 2 files changed, 54 insertions(+), 38 deletions(-) > > > > diff --git a/inany.h b/inany.h > > index 4e53da9..a677aa7 100644 > > --- a/inany.h > > +++ b/inany.h > > @@ -30,11 +30,11 @@ union inany_addr { > > * > > * Return: IPv4 address if @addr is IPv4, NULL otherwise > > */ > > -static inline const struct in_addr *inany_v4(const union inany_addr *addr) > > +static inline struct in_addr *inany_v4(const union inany_addr *addr) > > There must be a reason, but I can't understand why this change is > needed here. Because in tcp_snat_inbound() we want to modify, not just examine the IPv4 address within the IPv6 address. Ideally the return would be const if and only if the input is, but C can't express that. This appears to be the conventional half-arsed solution (see, e.g. memchr() or strstr()). > > { > > if (!IN6_IS_ADDR_V4MAPPED(&addr->a6)) > > return NULL; > > - return &addr->_v4mapped.a4; > > + return (struct in_addr *)&addr->_v4mapped.a4; > > } > > > > /** inany_equals - Compare two IPv[46] addresses > > @@ -66,3 +66,29 @@ static inline void inany_from_af(union inany_addr *aa, int af, const void *addr) > > assert(0); > > } > > } > > + > > +/** inany_from_sockaddr - Extract IPv[46] address and port number from sockaddr > > + * @a: Pointer to store IPv[46] address > > This is aa below, I'm not sure why. Fixed. > > + * @port: Pointer to store port number, host order > > + * @addr: struct sockaddr_in (IPv4) or struct sockaddr_in6 (IPv6) > > This became sa_ (needless to say, addr would make more sense). Good call, changed. > > + */ > > +static inline void inany_from_sockaddr(union inany_addr *aa, in_port_t *port, > > + const void *sa_) > > +{ > > + const struct sockaddr *sa = (const struct sockaddr *)sa_; > > + > > + 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); > > + } 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); > > + } else { > > + /* Not valid to call with other address families */ > > + assert(0); > > + } > > +} > > diff --git a/tcp.c b/tcp.c > > index b05ed6c..fca5df4 100644 > > --- a/tcp.c > > +++ b/tcp.c > > @@ -2724,6 +2724,29 @@ static void tcp_connect_finish(struct ctx *c, struct tcp_tap_conn *conn) > > conn_flag(c, conn, ACK_FROM_TAP_DUE); > > } > > > > +static void tcp_snat_inbound(const struct ctx *c, union inany_addr *addr) > > What this does is kind of obvious, still a comment would be nice. Good point, added. Especially since I'm hoping to share this with UDP at some later point. > > +{ > > + struct in_addr *addr4 = inany_v4(addr); > > + > > + if (addr4) { > > + if (IN4_IS_ADDR_LOOPBACK(addr4) || > > + IN4_IS_ADDR_UNSPECIFIED(addr4) || > > + IN4_ARE_ADDR_EQUAL(addr4, &c->ip4.addr_seen)) > > + *addr4 = c->ip4.gw; > > + } else { > > + struct in6_addr *addr6 = &addr->a6; > > + > > + if (IN6_IS_ADDR_LOOPBACK(addr6) || > > + IN6_ARE_ADDR_EQUAL(addr6, &c->ip6.addr_seen) || > > + IN6_ARE_ADDR_EQUAL(addr6, &c->ip6.addr)) { > > + if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw)) > > + *addr6 = c->ip6.gw; > > + else > > + *addr6 = c->ip6.addr_ll; > > + } > > + } > > +} > > + > > /** > > * tcp_tap_conn_from_sock() - Initialize state for non-spliced connection > > * @c: Execution context > > @@ -2744,43 +2767,10 @@ static void tcp_tap_conn_from_sock(struct ctx *c, union epoll_ref ref, > > conn->ws_to_tap = conn->ws_from_tap = 0; > > conn_event(c, conn, SOCK_ACCEPTED); > > > > - if (sa->sa_family == AF_INET6) { > > - struct sockaddr_in6 sa6; > > - > > - memcpy(&sa6, sa, sizeof(sa6)); > > - > > - if (IN6_IS_ADDR_LOOPBACK(&sa6.sin6_addr) || > > - IN6_ARE_ADDR_EQUAL(&sa6.sin6_addr, &c->ip6.addr_seen) || > > - IN6_ARE_ADDR_EQUAL(&sa6.sin6_addr, &c->ip6.addr)) { > > - struct in6_addr *src; > > + inany_from_sockaddr(&conn->addr, &conn->sock_port, sa); > > + conn->tap_port = ref.r.p.tcp.tcp.index; > > > > - if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw)) > > - src = &c->ip6.gw; > > - else > > - src = &c->ip6.addr_ll; > > - > > - memcpy(&sa6.sin6_addr, src, sizeof(*src)); > > - } > > - > > - inany_from_af(&conn->addr, AF_INET6, &sa6.sin6_addr); > > - > > - conn->sock_port = ntohs(sa6.sin6_port); > > - conn->tap_port = ref.r.p.tcp.tcp.index; > > - } else { > > - struct sockaddr_in sa4; > > - > > - memcpy(&sa4, sa, sizeof(sa4)); > > - > > - 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; > > - > > - inany_from_af(&conn->addr, AF_INET, &sa4.sin_addr); > > - > > - conn->sock_port = ntohs(sa4.sin_port); > > - conn->tap_port = ref.r.p.tcp.tcp.index; > > - } > > + tcp_snat_inbound(c, &conn->addr); > > > > tcp_seq_init(c, conn, now); > > tcp_hash_insert(c, conn); > -- 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