[git commit] udhcpc: fix BPF filter. Hopefully fixes the root cause of 4598 and 6746

Denys Vlasenko vda.linux at googlemail.com
Wed Feb 19 13:17:11 UTC 2014


commit: http://git.busybox.net/busybox/commit/?id=ffc3a93d0dbf4ac887f528c0495cd586a092d88f
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master

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

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 networking/udhcp/d6_dhcpc.c |    2 +-
 networking/udhcp/dhcpc.c    |    7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index b0f0798..044f046 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 bdb1e2b..25f18b3 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 = {


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