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udhcpc: don't use BPF filter, users report problems (bugs 4598, 6746)

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2014-02-03 18:03:42 +01:00
parent fe8390e0fe
commit e4785ca653
1 changed files with 46 additions and 47 deletions
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93
networking/udhcp/dhcpc.c
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@ -976,53 +976,6 @@ static int udhcp_raw_socket(int ifindex)
int fd;
struct sockaddr_ll sock;
/*
* Comment:
*
* I've selected not to see LL header, so BPF doesn't see it, too.
* The filter may also pass non-IP and non-ARP packets, but we do
* a more complete check when receiving the message in userspace.
*
* and filter shamelessly stolen from:
*
* http://www.flamewarmaster.de/software/dhcpclient/
*
* There are a few other interesting ideas on that page (look under
* "Motivation"). Use of netlink events is most interesting. Think
* of various network servers listening for events and reconfiguring.
* That would obsolete sending HUP signals and/or make use of restarts.
*
* Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
* License: GPL v2.
*
* TODO: make conditional?
*/
static const struct sock_filter filter_instr[] = {
/* load 9th byte (protocol) */
BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
/* jump to L1 if it is IPPROTO_UDP, else to L4 */
BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
/* L1: load halfword from offset 6 (flags and frag offset) */
BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
/* jump to L4 if any bits in frag offset field are set, else to L2 */
BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
/* L2: skip IP header (load index reg with header len) */
BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
/* load udp destination port from halfword[header_len + 2] */
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 */
BPF_STMT(BPF_RET|BPF_K, 0),
};
static const struct sock_fprog filter_prog = {
.len = sizeof(filter_instr) / sizeof(filter_instr[0]),
/* casting const away: */
.filter = (struct sock_filter *) filter_instr,
};
log1("Opening raw socket on ifindex %d", ifindex); //log2?
fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
@ -1033,13 +986,59 @@ static int udhcp_raw_socket(int ifindex)
sock.sll_ifindex = ifindex;
xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
#if 0 /* Several users reported breakage when BPF filter is used */
if (CLIENT_PORT == 68) {
/* Use only if standard port is in use */
/*
* I've selected not to see LL header, so BPF doesn't see it, too.
* The filter may also pass non-IP and non-ARP packets, but we do
* a more complete check when receiving the message in userspace.
*
* and filter shamelessly stolen from:
*
* http://www.flamewarmaster.de/software/dhcpclient/
*
* There are a few other interesting ideas on that page (look under
* "Motivation"). Use of netlink events is most interesting. Think
* of various network servers listening for events and reconfiguring.
* That would obsolete sending HUP signals and/or make use of restarts.
*
* Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
* License: GPL v2.
*
* TODO: make conditional?
*/
static const struct sock_filter filter_instr[] = {
/* load 9th byte (protocol) */
BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
/* jump to L1 if it is IPPROTO_UDP, else to L4 */
BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6),
/* L1: load halfword from offset 6 (flags and frag offset) */
BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6),
/* jump to L4 if any bits in frag offset field are set, else to L2 */
BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0),
/* L2: skip IP header (load index reg with header len) */
BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),
/* load udp destination port from halfword[header_len + 2] */
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 */
BPF_STMT(BPF_RET|BPF_K, 0),
};
static const struct sock_fprog filter_prog = {
.len = sizeof(filter_instr) / sizeof(filter_instr[0]),
/* casting const away: */
.filter = (struct sock_filter *) filter_instr,
};
/* Ignoring error (kernel may lack support for this) */
if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
sizeof(filter_prog)) >= 0)
log1("Attached filter to raw socket fd"); // log?
}
#endif
if (setsockopt(fd, SOL_PACKET, PACKET_AUXDATA,
&const_int_1, sizeof(int)) < 0