netfilter: nf_reject_ipv4: don't send tcp RST if the packet is non-TCP

In iptables, if the user add a rule to send tcp RST and specify the
non-TCP protocol, such as UDP, kernel will reject this request. But
in nftables, this validity check only occurs in nft tool, i.e. only
in userspace.

This means that user can add such a rule like follows via nfnetlink:
  "nft add rule filter forward ip protocol udp reject with tcp reset"

This will generate some confusing tcp RST packets. So we should send
tcp RST only when it is TCP packet.

Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
index b6ea57ec5e141837c587f571ad82d94e99ee382e..fd8220213afc36375f83d0af902443cf2f5a4a8f 100644 (file)
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -24,6 +24,9 @@ const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb,
        if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
                return NULL;
 
+       if (ip_hdr(oldskb)->protocol != IPPROTO_TCP)
+               return NULL;
+
        oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
                                 sizeof(struct tcphdr), _oth);
        if (oth == NULL)