bpf: Setup socket family and addresses in bpf_prog_test_run_skb

Now it's impossible to test all branches of cgroup_skb bpf program which
accesses skb->family and skb->{local,remote}_ip{4,6} fields because they
are zeroed during socket allocation. This commit fills socket family and
addresses from related fields in constructed skb.

Signed-off-by: Dmitry Yakunin <zeil@yandex-team.ru>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200803090545.82046-2-zeil@yandex-team.ru

net/bpf/test_run.c

@@ -449,6 +449,27 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
 	skb->protocol = eth_type_trans(skb, current->nsproxy->net_ns->loopback_dev);
 	skb_reset_network_header(skb);
 
+	switch (skb->protocol) {
+	case htons(ETH_P_IP):
+		sk->sk_family = AF_INET;
+		if (sizeof(struct iphdr) <= skb_headlen(skb)) {
+			sk->sk_rcv_saddr = ip_hdr(skb)->saddr;
+			sk->sk_daddr = ip_hdr(skb)->daddr;
+		}
+		break;
+#if IS_ENABLED(CONFIG_IPV6)
+	case htons(ETH_P_IPV6):
+		sk->sk_family = AF_INET6;
+		if (sizeof(struct ipv6hdr) <= skb_headlen(skb)) {
+			sk->sk_v6_rcv_saddr = ipv6_hdr(skb)->saddr;
+			sk->sk_v6_daddr = ipv6_hdr(skb)->daddr;
+		}
+		break;
+#endif
+	default:
+		break;
+	}
+
 	if (is_l2)
 		__skb_push(skb, hh_len);
 	if (is_direct_pkt_access)