udhcpc: fix BPF filter. Hopefully fixes the root cause of 4598 and 6746

Use a *signed* large positive value in BPF filter to indicate success.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 5 insertions, 4 deletions

diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index b0f0798e5..044f04673 100644
--- a/networking/udhcp/d6_dhcpc.c
+++ b/networking/udhcp/d6_dhcpc.c
@@ -711,7 +711,7 @@ static int d6_raw_socket(int ifindex)
                 /* jump to L3 if udp dport is CLIENT_PORT6, else to L4 */
                 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
                 /* L3: accept packet */
-                BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
+                BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
                 /* L4: discard packet */
                 BPF_STMT(BPF_RET|BPF_K, 0),
         };
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index bdb1e2b9b..25f18b35d 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -1025,9 +1025,10 @@ static int udhcp_raw_socket(int ifindex)
                         BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2),
                         /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */
                         BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1),
-                        /* L3: accept packet */
-                        BPF_STMT(BPF_RET|BPF_K, 0xffffffff),
-                        /* L4: discard packet */
+                        /* L3: accept packet ("accept 0x7fffffff bytes") */
+                        /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */
+                        BPF_STMT(BPF_RET|BPF_K, 0x7fffffff),
+                        /* L4: discard packet ("accept zero bytes") */
                         BPF_STMT(BPF_RET|BPF_K, 0),
                 };
                 static const struct sock_fprog filter_prog = {