On Tue, 10 Oct 2017 12:58:52 +0530 Christina Jacob <christina.jacob.koik...@gmail.com> wrote:
> +SEC("xdp3") > +int xdp_prog3(struct xdp_md *ctx) > +{ > + void *data_end = (void *)(long)ctx->data_end; > + void *data = (void *)(long)ctx->data; > + struct ethhdr *eth = data; > + int rc = XDP_DROP, forward_to; > + long *value; > + struct trie_value *prefix_value; > + long *dest_mac = NULL, *src_mac = NULL; > + u16 h_proto; > + u64 nh_off; > + u32 ipproto; > + union key_4 key4; Reverse-xmas tree rule: Prefer ordering declarations longest to shortest. [...] > + if (h_proto == htons(ETH_P_ARP)) { > + return XDP_PASS; > + } else if (h_proto == htons(ETH_P_IP)) { > + int src_ip = 0, dest_ip = 0; > + struct direct_map *direct_entry; > + > + ipproto = parse_ipv4(data, nh_off, data_end, &src_ip, &dest_ip); > + direct_entry = (struct direct_map *)bpf_map_lookup_elem > + (&exact_match, &dest_ip); > + /*check for exact match, this would give a faster lookup*/ > + if (direct_entry && direct_entry->mac && direct_entry->arp.mac) > { > + src_mac = &direct_entry->mac; > + dest_mac = &direct_entry->arp.mac; > + forward_to = direct_entry->ifindex; > + } else { > + /*Look up in the trie for lpm*/ > + key4.b32[0] = 32; > + key4.b8[4] = dest_ip % 0x100; > + key4.b8[5] = (dest_ip >> 8) % 0x100; > + key4.b8[6] = (dest_ip >> 16) % 0x100; > + key4.b8[7] = (dest_ip >> 24) % 0x100; > + prefix_value = ((struct trie_value *)bpf_map_lookup_elem > + (&lpm_map, &key4)); > + if (!prefix_value) { > + return XDP_DROP; > + } else { > + src_mac = &prefix_value->value; > + if (src_mac) { > + dest_mac = (long *)bpf_map_lookup_elem > + (&arp_table, &dest_ip); > + if (!dest_mac) { > + if (prefix_value->gw) { > + dest_ip = *(__be32 > *)&prefix_value->gw; > + dest_mac = (long > *)bpf_map_lookup_elem(&arp_table, &dest_ip); > + } else { > + return XDP_DROP; > + } > + } > + forward_to = prefix_value->ifindex; > + } else { > + return XDP_DROP; > + } > + } > + } > + } else { > + ipproto = 0; > + } The nesting in this function is getting annoying to read. Kernel code often use "early return" style coding to solve this. A quick search turns up this guide, look at section "Early return" https://en.wikibooks.org/wiki/Computer_Programming/Coding_Style/Minimize_nesting -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer