The limit max_conns_per_ip is broken

[ShikChen]

nsjail/net.c

Lines 165 to 178 in e2529ce

	unsigned int cnt = 0;
	struct pids_t* p;
	TAILQ_FOREACH(p, &nsjconf->pids, pointers) {
	if (memcmp(addr.sin6_addr.s6_addr, p->remote_addr.sin6_addr.s6_addr,
	sizeof(*p->remote_addr.sin6_addr.s6_addr)) == 0) {
	cnt++;
	}
	}
	if (cnt >= nsjconf->max_conns_per_ip) {
	LOG_W("Rejecting connection from '%s', max_conns_per_ip limit reached: %u", cs_addr,
	nsjconf->max_conns_per_ip);
	return false;
	}

There is a redundant dereference operator in the sizeof(...) of memcmp, so it would only compare the first byte of address and reject new connections too aggressively.

The relevant structures:

struct sockaddr_in6 {
    sa_family_t     sin6_family;   /* AF_INET6 */
    in_port_t       sin6_port;     /* port number */
    uint32_t        sin6_flowinfo; /* IPv6 flow information */
    struct in6_addr sin6_addr;     /* IPv6 address */
    uint32_t        sin6_scope_id; /* Scope ID (new in 2.4) */
};

struct in6_addr {
    unsigned char   s6_addr[16];   /* IPv6 address */
};

[robertswiecki]

Thanks for the report - fixed with 9e355cb