[connection-limit] XDP program assumes IPv4 and does not handle IPv6 packets

[alwaysanimesh]

Source code: eBPF-Package-Repository/connection-limit/connection_limit.bpf.c

Description:
While reviewing the XDP program (_xdp_limit_conn), I noticed that the code directly parses the packet as an IPv4 header without checking the Ethernet protocol type. This can lead to misparsing non-IPv4 packets.

    /* Check if its valid ethernet packet */
    if (data + sizeof(struct ethhdr)+ 1 > data_end)
        return XDP_PASS;

    /* Check if its valid ip packet */
    struct iphdr *iph = (struct iphdr *)(data + sizeof(struct ethhdr));

There is no validation of eth->h_proto before this cast.

Question:

1. Would it be appropriate to add an explicit EtherType check before parsing, for example:

if (ethhdr->h_proto != ETH_P_IP)
    return XDP_PASS;

to ensure that only IPv4 packets are interpreted as struct iphdr, and non-IPv4 are passed right away?

2. Whether the program is designed to run in an environment where only IPv4 packets reach this stage