On Wed, 16 Nov 2022 15:42:12 +1100 David Gibson <david(a)gibson.dropbear.id.au> wrote:Platforms like Linux allow IPv6 sockets to listen for IPv4 connections as well as native IPv6 connections. By doing this we halve the number of listening sockets we need for TCP (assuming passt/pasta is listening on the same ports for IPv4 and IPv6). When forwarding many ports (e.g. -t all) this can significantly reduce the amount of kernel memory that passt consumes. When forwarding all TCP and UDP ports for both IPv4 and IPv6 (-t all -u all), this reduces kernel memory usage from ~677MiB to ~487MiB (kernel version 6.0.8 on Fedora 37, x86_64).Oh, nice, that's quite significant.Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- tcp.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/tcp.c b/tcp.c index 616b9d0..5860c9f 100644 --- a/tcp.c +++ b/tcp.c @@ -2991,8 +2991,12 @@ static int tcp_sock_init_af(const struct ctx *c, int af, in_port_t port, s = sock_l4(c, af, IPPROTO_TCP, addr, ifname, port, tref.u32); - if (c->tcp.fwd_in.mode == FWD_AUTO) - tcp_sock_init_ext[port][(af == AF_INET) ? V4 : V6] = s; + if (c->tcp.fwd_in.mode == FWD_AUTO) { + if (af == AF_INET || af == AF_UNSPEC) + tcp_sock_init_ext[port][V4] = s; + if (af == AF_INET6 || af == AF_UNSPEC)Nit: you could align the || af == AF_UNSPEC above with an extra whitespace (as it's done in the context below).+ tcp_sock_init_ext[port][V6] = s; + } if (s < 0) return -1; @@ -3012,6 +3016,12 @@ static int tcp_sock_init_af(const struct ctx *c, int af, in_port_t port, void tcp_sock_init(const struct ctx *c, sa_family_t af, const void *addr, const char *ifname, in_port_t port) { + if (af == AF_UNSPEC && c->ifi4 && c->ifi6) + /* Attempt to get a dual stack socket */ + if (tcp_sock_init_af(c, AF_UNSPEC, port, addr, ifname) >= 0) + return; + + /* Otherwise create a socket per IP version */...this looks surprisingly clean by the way, at least much cleaner than I expected.if ((af == AF_INET || af == AF_UNSPEC) && c->ifi4) tcp_sock_init_af(c, AF_INET, port, addr, ifname); if ((af == AF_INET6 || af == AF_UNSPEC) && c->ifi6)I just finished reviewing this series, in general it looks great to me, I would have another look (and test!) on Thursday -- either using this version or a re-spin. -- Stefano