From 06bd2b1ed04ca9fdbc767859885944a1e8b86b40 Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Thu, 27 Oct 2016 18:51:55 -0400 Subject: [PATCH] tipc: fix broadcast link synchronization problem In commit 2d18ac4ba745 ("tipc: extend broadcast link initialization criteria") we tried to fix a problem with the initial synchronization of broadcast link acknowledge values. Unfortunately that solution is not sufficient to solve the issue. We have seen it happen that LINK_PROTOCOL/STATE packets with a valid non-zero unicast acknowledge number may bypass BCAST_PROTOCOL initialization, NAME_DISTRIBUTOR and other STATE packets with invalid broadcast acknowledge numbers, leading to premature opening of the broadcast link. When the bypassed packets finally arrive, they are inadvertently accepted, and the already correctly initialized acknowledge number in the broadcast receive link is overwritten by the invalid (zero) value of the said packets. After this the broadcast link goes stale. We now fix this by marking the packets where we know the acknowledge value is or may be invalid, and then ignoring the acks from those. To this purpose, we claim an unused bit in the header to indicate that the value is invalid. We set the bit to 1 in the initial BCAST_PROTOCOL synchronization packet and all initial ("bulk") NAME_DISTRIBUTOR packets, plus those LINK_PROTOCOL packets sent out before the broadcast links are fully synchronized. This minor protocol update is fully backwards compatible. Reported-by: John Thompson Tested-by: John Thompson Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/bcast.c | 14 ++++++++++---- net/tipc/bcast.h | 3 ++- net/tipc/link.c | 2 ++ net/tipc/msg.h | 17 +++++++++++++++++ net/tipc/name_distr.c | 1 + net/tipc/node.c | 2 +- 6 files changed, 33 insertions(+), 6 deletions(-) diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c index 753f774cb46f..aa1babbea385 100644 --- a/net/tipc/bcast.c +++ b/net/tipc/bcast.c @@ -247,11 +247,17 @@ int tipc_bcast_rcv(struct net *net, struct tipc_link *l, struct sk_buff *skb) * * RCU is locked, no other locks set */ -void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, u32 acked) +void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, + struct tipc_msg *hdr) { struct sk_buff_head *inputq = &tipc_bc_base(net)->inputq; + u16 acked = msg_bcast_ack(hdr); struct sk_buff_head xmitq; + /* Ignore bc acks sent by peer before bcast synch point was received */ + if (msg_bc_ack_invalid(hdr)) + return; + __skb_queue_head_init(&xmitq); tipc_bcast_lock(net); @@ -279,11 +285,11 @@ int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l, __skb_queue_head_init(&xmitq); tipc_bcast_lock(net); - if (msg_type(hdr) == STATE_MSG) { + if (msg_type(hdr) != STATE_MSG) { + tipc_link_bc_init_rcv(l, hdr); + } else if (!msg_bc_ack_invalid(hdr)) { tipc_link_bc_ack_rcv(l, msg_bcast_ack(hdr), &xmitq); rc = tipc_link_bc_sync_rcv(l, hdr, &xmitq); - } else { - tipc_link_bc_init_rcv(l, hdr); } tipc_bcast_unlock(net); diff --git a/net/tipc/bcast.h b/net/tipc/bcast.h index 5ffe34472ccd..855d53c64ab3 100644 --- a/net/tipc/bcast.h +++ b/net/tipc/bcast.h @@ -55,7 +55,8 @@ void tipc_bcast_dec_bearer_dst_cnt(struct net *net, int bearer_id); int tipc_bcast_get_mtu(struct net *net); int tipc_bcast_xmit(struct net *net, struct sk_buff_head *list); int tipc_bcast_rcv(struct net *net, struct tipc_link *l, struct sk_buff *skb); -void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, u32 acked); +void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, + struct tipc_msg *hdr); int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l, struct tipc_msg *hdr); int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg); diff --git a/net/tipc/link.c b/net/tipc/link.c index b36e16cdc945..1055164c6232 100644 --- a/net/tipc/link.c +++ b/net/tipc/link.c @@ -1312,6 +1312,7 @@ static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe, msg_set_next_sent(hdr, l->snd_nxt); msg_set_ack(hdr, l->rcv_nxt - 1); msg_set_bcast_ack(hdr, bcl->rcv_nxt - 1); + msg_set_bc_ack_invalid(hdr, !node_up); msg_set_last_bcast(hdr, l->bc_sndlink->snd_nxt - 1); msg_set_link_tolerance(hdr, tolerance); msg_set_linkprio(hdr, priority); @@ -1574,6 +1575,7 @@ static void tipc_link_build_bc_init_msg(struct tipc_link *l, __skb_queue_head_init(&list); if (!tipc_link_build_bc_proto_msg(l->bc_rcvlink, false, 0, &list)) return; + msg_set_bc_ack_invalid(buf_msg(skb_peek(&list)), true); tipc_link_xmit(l, &list, xmitq); } diff --git a/net/tipc/msg.h b/net/tipc/msg.h index c3832cdf2278..50a739860d37 100644 --- a/net/tipc/msg.h +++ b/net/tipc/msg.h @@ -714,6 +714,23 @@ static inline void msg_set_peer_stopping(struct tipc_msg *m, u32 s) msg_set_bits(m, 5, 13, 0x1, s); } +static inline bool msg_bc_ack_invalid(struct tipc_msg *m) +{ + switch (msg_user(m)) { + case BCAST_PROTOCOL: + case NAME_DISTRIBUTOR: + case LINK_PROTOCOL: + return msg_bits(m, 5, 14, 0x1); + default: + return false; + } +} + +static inline void msg_set_bc_ack_invalid(struct tipc_msg *m, bool invalid) +{ + msg_set_bits(m, 5, 14, 0x1, invalid); +} + static inline char *msg_media_addr(struct tipc_msg *m) { return (char *)&m->hdr[TIPC_MEDIA_INFO_OFFSET]; diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c index a04fe9be1c60..c1cfd92de17a 100644 --- a/net/tipc/name_distr.c +++ b/net/tipc/name_distr.c @@ -156,6 +156,7 @@ static void named_distribute(struct net *net, struct sk_buff_head *list, pr_warn("Bulk publication failure\n"); return; } + msg_set_bc_ack_invalid(buf_msg(skb), true); item = (struct distr_item *)msg_data(buf_msg(skb)); } diff --git a/net/tipc/node.c b/net/tipc/node.c index 7ef14e2d2356..9d2f4c2b08ab 100644 --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -1535,7 +1535,7 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b) if (unlikely(usr == LINK_PROTOCOL)) tipc_node_bc_sync_rcv(n, hdr, bearer_id, &xmitq); else if (unlikely(tipc_link_acked(n->bc_entry.link) != bc_ack)) - tipc_bcast_ack_rcv(net, n->bc_entry.link, bc_ack); + tipc_bcast_ack_rcv(net, n->bc_entry.link, hdr); /* Receive packet directly if conditions permit */ tipc_node_read_lock(n); -- 2.20.1