From: Roy Marples <roy@marples.name>
Date: Fri, 10 Mar 2017 08:36:26 +0000 (+0000)
Subject: bpf: only interested in direct conflict (sender) or ARP probes.
X-Git-Tag: v7.0.0-beta1~59
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8f5c2afc4ccca438f815f87ae9133ec7195ef22d;p=thirdparty%2Fdhcpcd.git

bpf: only interested in direct conflict (sender) or ARP probes.
---

diff --git a/bpf.c b/bpf.c
index c3e2ff58..73e83e28 100644
--- a/bpf.c
+++ b/bpf.c
@@ -417,7 +417,7 @@ static const struct bpf_insn bpf_arp_filter [] = {
 	BPF_STMT(BPF_RET + BPF_K, 0),
 };
 #define bpf_arp_filter_len	__arraycount(bpf_arp_filter)
-#define bpf_arp_extra		((ARP_ADDRS_MAX * 2) * 2) + 2
+#define bpf_arp_extra		(((ARP_ADDRS_MAX + 1) * 2) * 2) + 2
 
 int
 bpf_arp(struct interface *ifp, int fd)
@@ -473,6 +473,13 @@ bpf_arp(struct interface *ifp, int fd)
 			bp++;
 		}
 
+		/* If we didn't match sender, then we're only interested in
+		 * ARP probes to us, so check the null host sender. */
+		BPF_SET_JUMP(bp, BPF_JMP + BPF_JEQ + BPF_K, INADDR_ANY, 1, 0);
+		bp++;
+		BPF_SET_STMT(bp, BPF_RET + BPF_K, 0);
+		bp++;
+
 		/* Match target protocol address */
 		BPF_SET_STMT(bp, BPF_LD + BPF_W + BPF_IND,
 		             (sizeof(struct arphdr)