[PATCH gwproxy v1 2/2] dns: validate restyp on initialization

[Ahmad Gani <reyuki@gnuweeb.org>]

Return EINVAL on initialization if restyp is invalid.
And then prefer ipv4 if GWP_DNS_RESTYP_DEFAULT is used.

Fixes: 82c86a7256d6 ("gwproxy/dns: Replace the old DNS cache system with a new one.")
Signed-off-by: Ahmad Gani <reyuki@gnuweeb.org>
---
 src/gwproxy/dns.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/gwproxy/dns.c b/src/gwproxy/dns.c
index f7cbcb2d6e89..b189b33127af 100644
--- a/src/gwproxy/dns.c
+++ b/src/gwproxy/dns.c
@@ -619,7 +619,8 @@ static int fetch_addr(struct gwp_dns_cache_entry *e, struct gwp_sockaddr *addr,
 			if (!fetch_i4(e, addr, port))
 				return -EHOSTUNREACH;
 		}
-	} else if (restyp == GWP_DNS_RESTYP_PREFER_IPV4) {
+	} else if (restyp == GWP_DNS_RESTYP_PREFER_IPV4 ||
+		   restyp == GWP_DNS_RESTYP_DEFAULT) {
 		if (!fetch_i4(e, addr, port)) {
 			if (!fetch_i6(e, addr, port))
 				return -EHOSTUNREACH;
@@ -679,11 +680,28 @@ static void free_cache(struct gwp_dns_cache *cache)
 	cache = NULL;
 }
 
+static inline bool validate_restyp(int restyp)
+{
+	switch (restyp) {
+	case GWP_DNS_RESTYP_DEFAULT:
+	case GWP_DNS_RESTYP_IPV4_ONLY:
+	case GWP_DNS_RESTYP_IPV6_ONLY:
+	case GWP_DNS_RESTYP_PREFER_IPV4:
+	case GWP_DNS_RESTYP_PREFER_IPV6:
+		return true;
+	default:
+		return false;
+	}
+}
+
 int gwp_dns_ctx_init(struct gwp_dns_ctx **ctx_p, const struct gwp_dns_cfg *cfg)
 {
 	struct gwp_dns_ctx *ctx;
 	int r;
 
+	if (!validate_restyp(cfg->restyp))
+		return -EINVAL;
+
 	ctx = calloc(1, sizeof(*ctx));
 	if (!ctx)
 		return -ENOMEM;
-- 
Ahmad Gani