diff options
| -rw-r--r-- | fwd.c | 18 | ||||
| -rw-r--r-- | passt.1 | 10 |
2 files changed, 21 insertions, 7 deletions
@@ -157,6 +157,20 @@ void fwd_scan_ports_init(struct ctx *c) } /** + * is_dns_flow() - Determine if flow appears to be a DNS request + * @proto: Protocol (IP L4 protocol number) + * @ini: Flow address information of the initiating side + * + * Return: true if the flow appears to be directed at a dns server, that is a + * TCP or UDP flow to port 53 (domain) or port 853 (domain-s) + */ +static bool is_dns_flow(uint8_t proto, const struct flowside *ini) +{ + return ((proto == IPPROTO_UDP) || (proto == IPPROTO_TCP)) && + ((ini->fport == 53) || (ini->fport == 853)); +} + +/** * fwd_nat_from_tap() - Determine to forward a flow from the tap interface * @c: Execution context * @proto: Protocol (IP L4 protocol number) @@ -169,10 +183,10 @@ void fwd_scan_ports_init(struct ctx *c) uint8_t fwd_nat_from_tap(const struct ctx *c, uint8_t proto, const struct flowside *ini, struct flowside *tgt) { - if (proto == IPPROTO_UDP && ini->fport == 53 && + if (is_dns_flow(proto, ini) && inany_equals4(&ini->faddr, &c->ip4.dns_match)) tgt->eaddr = inany_from_v4(c->ip4.dns_host); - else if (proto == IPPROTO_UDP && ini->fport == 53 && + else if (is_dns_flow(proto, ini) && inany_equals6(&ini->faddr, &c->ip6.dns_match)) tgt->eaddr.a6 = c->ip6.dns_host; else if (!c->no_map_gw && inany_equals4(&ini->faddr, &c->ip4.gw)) @@ -244,11 +244,11 @@ usage of DNS addresses altogether. .TP .BR \-\-dns-forward " " \fIaddr -Map \fIaddr\fR (IPv4 or IPv6) as seen from guest or namespace to the first -configured DNS resolver (with corresponding IP version). Mapping is limited to -UDP traffic directed to port 53, and DNS answers are translated back with a -reverse mapping. -This option can be specified zero to two times (once for IPv4, once for IPv6). +Map \fIaddr\fR (IPv4 or IPv6) as seen from guest or namespace to the +first configured DNS resolver (with corresponding IP version). Maps +only UDP and TCP traffic to port 53 or port 853. Replies are +translated back with a reverse mapping. This option can be specified +zero to two times (once for IPv4, once for IPv6). .TP .BR \-S ", " \-\-search " " \fIlist |