Fix v6 source (remote) and dest (local) address

For v6, tcpdrop.py would report the source and destination addresses incorrectly - tcp_drop() covers the input path, where the source of the received packet is the daddr stored in the socket, while the destination of the received packet is the local address. This commit swaps them to be correct and leaves a comment since it is not obvious.
drcwr · Sep 30, 2020 · 7e3f0c0 · 7e3f0c0
1 parent 788303e
commit 7e3f0c0
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/tools/tcpdrop.py b/tools/tcpdrop.py
@@ -128,10 +128,12 @@
  struct ipv6_data_t data6 = {};
  data6.pid = pid;
  data6.ip = 6;
+ // The remote address (skc_v6_daddr) was the source
  bpf_probe_read_kernel(&data6.saddr, sizeof(data6.saddr),
- sk->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
- bpf_probe_read_kernel(&data6.daddr, sizeof(data6.daddr),
  sk->__sk_common.skc_v6_daddr.in6_u.u6_addr32);
+ // The local address (skc_v6_rcv_saddr) was the destination
+ bpf_probe_read_kernel(&data6.daddr, sizeof(data6.daddr),
+ sk->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
  data6.dport = dport;
  data6.sport = sport;
  data6.state = state;