From 744676e777207f4992ba4cc728a8a71352963c5b Mon Sep 17 00:00:00 2001 From: Matteo Croce Date: Sat, 15 Feb 2020 14:20:56 +0100 Subject: [PATCH] openvswitch: add TTL decrement action New action to decrement TTL instead of setting it to a fixed value. This action will decrement the TTL and, in case of expired TTL, drop it or execute an action passed via a nested attribute. The default TTL expired action is to drop the packet. Supports both IPv4 and IPv6 via the ttl and hop_limit fields, respectively. Tested with a corresponding change in the userspace: # ovs-dpctl dump-flows in_port(2),eth(),eth_type(0x0800), packets:0, bytes:0, used:never, actions:dec_ttl{ttl<=1 action:(drop)},1 in_port(1),eth(),eth_type(0x0800), packets:0, bytes:0, used:never, actions:dec_ttl{ttl<=1 action:(drop)},2 in_port(1),eth(),eth_type(0x0806), packets:0, bytes:0, used:never, actions:2 in_port(2),eth(),eth_type(0x0806), packets:0, bytes:0, used:never, actions:1 # ping -c1 192.168.0.2 -t 42 IP (tos 0x0, ttl 41, id 61647, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.0.1 > 192.168.0.2: ICMP echo request, id 386, seq 1, length 64 # ping -c1 192.168.0.2 -t 120 IP (tos 0x0, ttl 119, id 62070, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.0.1 > 192.168.0.2: ICMP echo request, id 388, seq 1, length 64 # ping -c1 192.168.0.2 -t 1 # Co-developed-by: Bindiya Kurle Signed-off-by: Bindiya Kurle Signed-off-by: Matteo Croce Acked-by: Pravin B Shelar Signed-off-by: David S. Miller --- include/uapi/linux/openvswitch.h | 7 ++++ net/openvswitch/actions.c | 67 ++++++++++++++++++++++++++++++ net/openvswitch/flow_netlink.c | 70 ++++++++++++++++++++++++++++++++ 3 files changed, 144 insertions(+) diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h index ae2bff14e7e1..9b14519e74d9 100644 --- a/include/uapi/linux/openvswitch.h +++ b/include/uapi/linux/openvswitch.h @@ -958,6 +958,7 @@ enum ovs_action_attr { OVS_ACTION_ATTR_CLONE, /* Nested OVS_CLONE_ATTR_*. */ OVS_ACTION_ATTR_CHECK_PKT_LEN, /* Nested OVS_CHECK_PKT_LEN_ATTR_*. */ OVS_ACTION_ATTR_ADD_MPLS, /* struct ovs_action_add_mpls. */ + OVS_ACTION_ATTR_DEC_TTL, /* Nested OVS_DEC_TTL_ATTR_*. */ __OVS_ACTION_ATTR_MAX, /* Nothing past this will be accepted * from userspace. */ @@ -1050,4 +1051,10 @@ struct ovs_zone_limit { __u32 count; }; +enum ovs_dec_ttl_attr { + OVS_DEC_TTL_ATTR_UNSPEC, + OVS_DEC_TTL_ATTR_ACTION, /* Nested struct nlattr */ + __OVS_DEC_TTL_ATTR_MAX +}; + #endif /* _LINUX_OPENVSWITCH_H */ diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c index 7fbfe2adfffa..fc0efd8833c8 100644 --- a/net/openvswitch/actions.c +++ b/net/openvswitch/actions.c @@ -964,6 +964,25 @@ static int output_userspace(struct datapath *dp, struct sk_buff *skb, return ovs_dp_upcall(dp, skb, key, &upcall, cutlen); } +static int dec_ttl_exception_handler(struct datapath *dp, struct sk_buff *skb, + struct sw_flow_key *key, + const struct nlattr *attr, bool last) +{ + /* The first action is always 'OVS_DEC_TTL_ATTR_ARG'. */ + struct nlattr *dec_ttl_arg = nla_data(attr); + int rem = nla_len(attr); + + if (nla_len(dec_ttl_arg)) { + struct nlattr *actions = nla_next(dec_ttl_arg, &rem); + + if (actions) + return clone_execute(dp, skb, key, 0, actions, rem, + last, false); + } + consume_skb(skb); + return 0; +} + /* When 'last' is true, sample() should always consume the 'skb'. * Otherwise, sample() should keep 'skb' intact regardless what * actions are executed within sample(). @@ -1180,6 +1199,45 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb, nla_len(actions), last, clone_flow_key); } +static int execute_dec_ttl(struct sk_buff *skb, struct sw_flow_key *key) +{ + int err; + + if (skb->protocol == htons(ETH_P_IPV6)) { + struct ipv6hdr *nh; + + err = skb_ensure_writable(skb, skb_network_offset(skb) + + sizeof(*nh)); + if (unlikely(err)) + return err; + + nh = ipv6_hdr(skb); + + if (nh->hop_limit <= 1) + return -EHOSTUNREACH; + + key->ip.ttl = --nh->hop_limit; + } else { + struct iphdr *nh; + u8 old_ttl; + + err = skb_ensure_writable(skb, skb_network_offset(skb) + + sizeof(*nh)); + if (unlikely(err)) + return err; + + nh = ip_hdr(skb); + if (nh->ttl <= 1) + return -EHOSTUNREACH; + + old_ttl = nh->ttl--; + csum_replace2(&nh->check, htons(old_ttl << 8), + htons(nh->ttl << 8)); + key->ip.ttl = nh->ttl; + } + return 0; +} + /* Execute a list of actions against 'skb'. */ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb, struct sw_flow_key *key, @@ -1365,6 +1423,15 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb, break; } + + case OVS_ACTION_ATTR_DEC_TTL: + err = execute_dec_ttl(skb, key); + if (err == -EHOSTUNREACH) { + err = dec_ttl_exception_handler(dp, skb, key, + a, true); + return err; + } + break; } if (unlikely(err)) { diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c index 7da4230627f5..1ccd5e092bca 100644 --- a/net/openvswitch/flow_netlink.c +++ b/net/openvswitch/flow_netlink.c @@ -80,6 +80,7 @@ static bool actions_may_change_flow(const struct nlattr *actions) case OVS_ACTION_ATTR_METER: case OVS_ACTION_ATTR_CHECK_PKT_LEN: case OVS_ACTION_ATTR_ADD_MPLS: + case OVS_ACTION_ATTR_DEC_TTL: default: return true; } @@ -2495,6 +2496,39 @@ static int validate_and_copy_sample(struct net *net, const struct nlattr *attr, return 0; } +static int validate_and_copy_dec_ttl(struct net *net, + const struct nlattr *attr, + const struct sw_flow_key *key, + struct sw_flow_actions **sfa, + __be16 eth_type, __be16 vlan_tci, + u32 mpls_label_count, bool log) +{ + int start, err; + u32 nested = true; + + if (!nla_len(attr)) + return ovs_nla_add_action(sfa, OVS_ACTION_ATTR_DEC_TTL, + NULL, 0, log); + + start = add_nested_action_start(sfa, OVS_ACTION_ATTR_DEC_TTL, log); + if (start < 0) + return start; + + err = ovs_nla_add_action(sfa, OVS_DEC_TTL_ATTR_ACTION, &nested, + sizeof(nested), log); + + if (err) + return err; + + err = __ovs_nla_copy_actions(net, attr, key, sfa, eth_type, + vlan_tci, mpls_label_count, log); + if (err) + return err; + + add_nested_action_end(*sfa, start); + return 0; +} + static int validate_and_copy_clone(struct net *net, const struct nlattr *attr, const struct sw_flow_key *key, @@ -3007,6 +3041,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, [OVS_ACTION_ATTR_CLONE] = (u32)-1, [OVS_ACTION_ATTR_CHECK_PKT_LEN] = (u32)-1, [OVS_ACTION_ATTR_ADD_MPLS] = sizeof(struct ovs_action_add_mpls), + [OVS_ACTION_ATTR_DEC_TTL] = (u32)-1, }; const struct ovs_action_push_vlan *vlan; int type = nla_type(a); @@ -3267,6 +3302,15 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr, break; } + case OVS_ACTION_ATTR_DEC_TTL: + err = validate_and_copy_dec_ttl(net, a, key, sfa, + eth_type, vlan_tci, + mpls_label_count, log); + if (err) + return err; + skip_copy = true; + break; + default: OVS_NLERR(log, "Unknown Action type %d", type); return -EINVAL; @@ -3438,6 +3482,26 @@ out: return err; } +static int dec_ttl_action_to_attr(const struct nlattr *attr, + struct sk_buff *skb) +{ + int err = 0, rem = nla_len(attr); + struct nlattr *start; + + start = nla_nest_start_noflag(skb, OVS_ACTION_ATTR_DEC_TTL); + + if (!start) + return -EMSGSIZE; + + err = ovs_nla_put_actions(nla_data(attr), rem, skb); + if (err) + nla_nest_cancel(skb, start); + else + nla_nest_end(skb, start); + + return err; +} + static int set_action_to_attr(const struct nlattr *a, struct sk_buff *skb) { const struct nlattr *ovs_key = nla_data(a); @@ -3538,6 +3602,12 @@ int ovs_nla_put_actions(const struct nlattr *attr, int len, struct sk_buff *skb) return err; break; + case OVS_ACTION_ATTR_DEC_TTL: + err = dec_ttl_action_to_attr(a, skb); + if (err) + return err; + break; + default: if (nla_put(skb, type, nla_len(a), nla_data(a))) return -EMSGSIZE;