On Mon, 6 Nov 2023 13:17:08 +1100 David Gibson <david(a)gibson.dropbear.id.au> wrote:udp uses the udp_tap_map, udp_splice_ns and udp_splice_init tables to keep track of already opened sockets bound to specific ports. We need a way to indicate entries where a socket hasn't been opened, but the code isn't consistent if this is indicated by a 0 or a -1: * udp_splice_sendfrom() and udp_tap_handler() assume that 0 indicates an unopened socket * udp_sock_init() fills in -1 for a failure to open a socket * udp_timer_one() is somewhere in between, treating only strictly positive fds as valid -1 (or, at least, negative) is really the correct choice here, since 0 is a theoretically valid fd value (if very unlikely in practice).Not so unlikely, actually (see also commit 6943d41d6cd0, where I missed to fix the UDP equivalents). By default we close standard input after initialising the "tap" file descriptor, so, depending on configuration options, zero might very well happen to be a UDP socket. I even pondered for a while to open a dummy file descriptor after closing standard input just for the sake of having zero as a "reserved" value, but it's not guaranteed to work.Change to use that consistently throughout. The table does need to be initialised to all -1 values before any calls to udp_sock_init() which can happen from conf_ports(). Because C doesn't make it easy to statically initialise non zero values in large tables, this does require a somewhat awkward call to initialise the table from conf(). This is the best approach I could see for the short term, with any luck it will go away at some point when those socket tables are replaced by a unified flow table. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 1 + udp.c | 26 +++++++++++++++++++++----- udp.h | 1 + 3 files changed, 23 insertions(+), 5 deletions(-) diff --git a/conf.c b/conf.c index a235b31..95b3e4b 100644 --- a/conf.c +++ b/conf.c @@ -1740,6 +1740,7 @@ void conf(struct ctx *c, int argc, char **argv) c->no_map_gw = 1; /* Inbound port options can be parsed now (after IPv4/IPv6 settings) */ + udp_portmap_clear(); optind = 1; do { name = getopt_long(argc, argv, optstring, options, NULL); diff --git a/udp.c b/udp.c index cadf393..a8473e3 100644 --- a/udp.c +++ b/udp.c @@ -238,6 +238,20 @@ static struct sockaddr_in6 udp6_localname = { static struct mmsghdr udp4_mh_splice [UDP_MAX_FRAMES]; static struct mmsghdr udp6_mh_splice [UDP_MAX_FRAMES]; +/** + * udp_portmap_clear() - Clear UDP port map before configuration + */ +void udp_portmap_clear(void) +{ + unsigned i; + + for (i = 0; i < NUM_PORTS; i++) { + udp_tap_map[V4][i].sock = udp_tap_map[V6][i].sock = -1; + udp_splice_ns[V4][i].sock = udp_splice_ns[V6][i].sock = -1; + udp_splice_init[V4][i].sock = udp_splice_init[V6][i].sock = -1; + } +}For TCP we do: $ grep memset\(.*0xff tcp.c tcp_splice.c tcp.c: memset(init_sock_pool4, 0xff, sizeof(init_sock_pool4)); tcp.c: memset(init_sock_pool6, 0xff, sizeof(init_sock_pool6)); tcp.c: memset(tcp_sock_init_ext, 0xff, sizeof(tcp_sock_init_ext)); tcp.c: memset(tcp_sock_ns, 0xff, sizeof(tcp_sock_ns)); tcp_splice.c: memset(splice_pipe_pool, 0xff, sizeof(splice_pipe_pool)); tcp_splice.c: memset(&ns_sock_pool4, 0xff, sizeof(ns_sock_pool4)); tcp_splice.c: memset(&ns_sock_pool6, 0xff, sizeof(ns_sock_pool6)); ...given how common this is, perhaps we could introduce a helper. In any case, I'll go ahead and apply this now, as the issue is quite bad, we can change this detail later. -- Stefano