[RFC PATCH net-next v5 2/6] gtp: Implement GTP echo response

From: Wojciech Drewek <wojciech.drewek(a)intel.com> Adding GTP device through ip link creates the situation where there is no userspace daemon which would handle GTP messages (Echo Request for example). GTP-U instance which would not respond to echo requests would violate GTP specification. When GTP packet arrives with GTP_ECHO_REQ message type, GTP_ECHO_RSP is send to the sender. GTP_ECHO_RSP message should contain information element with GTPIE_RECOVERY tag and restart counter value. For GTPv1 restart counter is not used and should be equal to 0, for GTPv0 restart counter contains information provided from userspace(IFLA_GTP_RESTART_COUNT). Signed-off-by: Wojciech Drewek <wojciech.drewek(a)intel.com> --- drivers/net/gtp.c | 212 ++++++++++++++++++++++++++++++++--- include/net/gtp.h | 31 +++++ include/uapi/linux/if_link.h | 1 + 3 files changed, 228 insertions(+), 16 deletions(-) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 29978c5e37e8..a51782868d23 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -75,6 +75,8 @@ struct gtp_dev { unsigned int hash_size; struct hlist_head *tid_hash; struct hlist_head *addr_hash; + + u8 restart_count; }; static unsigned int gtp_net_id __read_mostly; @@ -217,6 +219,106 @@ static int gtp_rx(struct pdp_ctx *pctx, struct sk_buff *skb, return -1; } +static struct rtable *ip4_route_output_gtp(struct flowi4 *fl4, + const struct sock *sk, + __be32 daddr, __be32 saddr) +{ + memset(fl4, 0, sizeof(*fl4)); + fl4->flowi4_oif = sk->sk_bound_dev_if; + fl4->daddr = daddr; + fl4->saddr = saddr; + fl4->flowi4_tos = RT_CONN_FLAGS(sk); + fl4->flowi4_proto = sk->sk_protocol; + + return ip_route_output_key(sock_net(sk), fl4); +} + +/* GSM TS 09.60. 7.3 + * In all Path Management messages: + * - TID: is not used and shall be set to 0. + * - Flow Label is not used and shall be set to 0 + * In signalling messages: + * - number: this field is not yet used in signalling messages. + * It shall be set to 255 by the sender and shall be ignored + * by the receiver + * Returns true if the echo req was correct, false otherwise. + */ +static bool gtp0_validate_echo_req(struct gtp0_header *gtp0) +{ + return !(gtp0->tid || (gtp0->flags ^ 0x1e) || + gtp0->number != 0xff || gtp0->flow); +} + +static int gtp0_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb) +{ + struct gtp0_packet *gtp_pkt; + struct gtp0_header *gtp0; + struct rtable *rt; + struct flowi4 fl4; + struct iphdr *iph; + __be16 seq; + + gtp0 = (struct gtp0_header *)(skb->data + sizeof(struct udphdr)); + + if (!gtp0_validate_echo_req(gtp0)) + return -1; + + seq = gtp0->seq; + + /* pull GTP and UDP headers */ + skb_pull_data(skb, sizeof(struct gtp0_header) + sizeof(struct udphdr)); + + gtp_pkt = skb_push(skb, sizeof(struct gtp0_packet)); + memset(gtp_pkt, 0, sizeof(struct gtp0_packet)); + + gtp_pkt->gtp0_h.flags = 0x1e; /* v0, GTP-non-prime. */ + gtp_pkt->gtp0_h.type = GTP_ECHO_RSP; + gtp_pkt->gtp0_h.length = + htons(sizeof(struct gtp0_packet) - sizeof(struct gtp0_header)); + + /* GSM TS 09.60. 7.3 The Sequence Number in a signalling response + * message shall be copied from the signalling request message + * that the GSN is replying to. + */ + gtp_pkt->gtp0_h.seq = seq; + + /* GSM TS 09.60. 7.3 In all Path Management Flow Label and TID + * are not used and shall be set to 0. + */ + gtp_pkt->gtp0_h.flow = 0; + gtp_pkt->gtp0_h.tid = 0; + gtp_pkt->gtp0_h.number = 0xff; + gtp_pkt->gtp0_h.spare[0] = 0xff; + gtp_pkt->gtp0_h.spare[1] = 0xff; + gtp_pkt->gtp0_h.spare[2] = 0xff; + + gtp_pkt->ie.tag = GTPIE_RECOVERY; + gtp_pkt->ie.val = gtp->restart_count; + + iph = ip_hdr(skb); + + /* find route to the sender, + * src address becomes dst address and vice versa. + */ + rt = ip4_route_output_gtp(&fl4, gtp->sk0, iph->saddr, iph->daddr); + if (IS_ERR(rt)) { + netdev_dbg(gtp->dev, "no route for echo response from %pI4\n", + &iph->saddr); + return -1; + } + + udp_tunnel_xmit_skb(rt, gtp->sk0, skb, + fl4.saddr, fl4.daddr, + iph->tos, + ip4_dst_hoplimit(&rt->dst), + 0, + htons(GTP0_PORT), htons(GTP0_PORT), + !net_eq(sock_net(gtp->sk1u), + dev_net(gtp->dev)), + false); + return 0; +} + /* 1 means pass up to the stack, -1 means drop and 0 means decapsulated. */ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb) { @@ -233,6 +335,13 @@ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb) if ((gtp0->flags >> 5) != GTP_V0) return 1; + /* If the sockets were created in kernel, it means that + * there is no daemon running in userspace which would + * handle echo request. + */ + if (gtp0->type == GTP_ECHO_REQ && gtp->sk_created) + return gtp0_echo_resp(gtp, skb); + if (gtp0->type != GTP_TPDU) return 1; @@ -245,6 +354,74 @@ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb) return gtp_rx(pctx, skb, hdrlen, gtp->role); } +static int gtp1u_echo_resp(struct gtp_dev *gtp, struct sk_buff *skb) +{ + struct gtp1_header_long *gtp1u; + struct gtp1u_packet *gtp_pkt; + struct rtable *rt; + struct flowi4 fl4; + struct iphdr *iph; + + gtp1u = (struct gtp1_header_long *)(skb->data + sizeof(struct udphdr)); + + /* 3GPP TS 29.281 5.1 - For the Echo Request, Echo Response, + * Error Indication and Supported Extension Headers Notification + * messages, the S flag shall be set to 1 and TEID shall be set to 0. + */ + if (!(gtp1u->flags & GTP1_F_SEQ) || gtp1u->tid) + return -1; + + /* pull GTP and UDP headers */ + skb_pull_data(skb, sizeof(struct gtp1_header_long) + sizeof(struct udphdr)); + + gtp_pkt = skb_push(skb, sizeof(struct gtp1u_packet)); + memset(gtp_pkt, 0, sizeof(struct gtp1u_packet)); + + /* S flag must be set to 1 */ + gtp_pkt->gtp1u_h.flags = 0x32; + gtp_pkt->gtp1u_h.type = GTP_ECHO_RSP; + /* seq, npdu and next should be counted to the length of the GTP packet + * that's why szie of gtp1_header should be subtracted, + * not why szie of gtp1_header_long. + */ + gtp_pkt->gtp1u_h.length = + htons(sizeof(struct gtp1u_packet) - sizeof(struct gtp1_header)); + /* 3GPP TS 29.281 5.1 - TEID has to be set to 0 */ + gtp_pkt->gtp1u_h.tid = 0; + + /* 3GPP TS 29.281 7.7.2 - The Restart Counter value in the + * Recovery information element shall not be used, i.e. it shall + * be set to zero by the sender and shall be ignored by the receiver. + * The Recovery information element is mandatory due to backwards + * compatibility reasons. + */ + gtp_pkt->ie.tag = GTPIE_RECOVERY; + gtp_pkt->ie.val = 0; + + iph = ip_hdr(skb); + + /* find route to the sender, + * src address becomes dst address and vice versa. + */ + rt = ip4_route_output_gtp(&fl4, gtp->sk1u, iph->saddr, iph->daddr); + if (IS_ERR(rt)) { + netdev_dbg(gtp->dev, "no route for echo response from %pI4\n", + &iph->saddr); + return -1; + } + + udp_tunnel_xmit_skb(rt, gtp->sk1u, skb, + fl4.saddr, fl4.daddr, + iph->tos, + ip4_dst_hoplimit(&rt->dst), + 0, + htons(GTP1U_PORT), htons(GTP1U_PORT), + !net_eq(sock_net(gtp->sk1u), + dev_net(gtp->dev)), + false); + return 0; +} + static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb) { unsigned int hdrlen = sizeof(struct udphdr) + @@ -260,6 +437,13 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb) if ((gtp1->flags >> 5) != GTP_V1) return 1; + /* If the sockets were created in kernel, it means that + * there is no daemon running in userspace which would + * handle echo request. + */ + if (gtp1->type == GTP_ECHO_REQ && gtp->sk_created) + return gtp1u_echo_resp(gtp, skb); + if (gtp1->type != GTP_TPDU) return 1; @@ -398,20 +582,6 @@ static void gtp_dev_uninit(struct net_device *dev) free_percpu(dev->tstats); } -static struct rtable *ip4_route_output_gtp(struct flowi4 *fl4, - const struct sock *sk, - __be32 daddr) -{ - memset(fl4, 0, sizeof(*fl4)); - fl4->flowi4_oif = sk->sk_bound_dev_if; - fl4->daddr = daddr; - fl4->saddr = inet_sk(sk)->inet_saddr; - fl4->flowi4_tos = RT_CONN_FLAGS(sk); - fl4->flowi4_proto = sk->sk_protocol; - - return ip_route_output_key(sock_net(sk), fl4); -} - static inline void gtp0_push_header(struct sk_buff *skb, struct pdp_ctx *pctx) { int payload_len = skb->len; @@ -517,7 +687,8 @@ static int gtp_build_skb_ip4(struct sk_buff *skb, struct net_device *dev, } netdev_dbg(dev, "found PDP context %p\n", pctx); - rt = ip4_route_output_gtp(&fl4, pctx->sk, pctx->peer_addr_ip4.s_addr); + rt = ip4_route_output_gtp(&fl4, pctx->sk, pctx->peer_addr_ip4.s_addr, + inet_sk(pctx->sk)->inet_saddr); if (IS_ERR(rt)) { netdev_dbg(dev, "no route to SSGN %pI4\n", &pctx->peer_addr_ip4.s_addr); @@ -848,6 +1019,11 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev, } gtp->role = role; + if (!data[IFLA_GTP_RESTART_COUNT]) + gtp->restart_count = 0; + else + gtp->restart_count = nla_get_u8(data[IFLA_GTP_RESTART_COUNT]); + gtp->net = src_net; err = gtp_hashtable_new(gtp, hashsize); @@ -903,6 +1079,7 @@ static const struct nla_policy gtp_policy[IFLA_GTP_MAX + 1] = { [IFLA_GTP_PDP_HASHSIZE] = { .type = NLA_U32 }, [IFLA_GTP_ROLE] = { .type = NLA_U32 }, [IFLA_GTP_CREATE_SOCKETS] = { .type = NLA_U8 }, + [IFLA_GTP_RESTART_COUNT] = { .type = NLA_U8 }, }; static int gtp_validate(struct nlattr *tb[], struct nlattr *data[], @@ -917,7 +1094,8 @@ static int gtp_validate(struct nlattr *tb[], struct nlattr *data[], static size_t gtp_get_size(const struct net_device *dev) { return nla_total_size(sizeof(__u32)) + /* IFLA_GTP_PDP_HASHSIZE */ - nla_total_size(sizeof(__u32)); /* IFLA_GTP_ROLE */ + nla_total_size(sizeof(__u32)) + /* IFLA_GTP_ROLE */ + nla_total_size(sizeof(__u8)); /* IFLA_GTP_RESTART_COUNT */ } static int gtp_fill_info(struct sk_buff *skb, const struct net_device *dev) @@ -928,6 +1106,8 @@ static int gtp_fill_info(struct sk_buff *skb, const struct net_device *dev) goto nla_put_failure; if (nla_put_u32(skb, IFLA_GTP_ROLE, gtp->role)) goto nla_put_failure; + if (nla_put_u8(skb, IFLA_GTP_RESTART_COUNT, gtp->restart_count)) + goto nla_put_failure; return 0; diff --git a/include/net/gtp.h b/include/net/gtp.h index 0e16ebb2a82d..0e12c37f2958 100644 --- a/include/net/gtp.h +++ b/include/net/gtp.h @@ -7,8 +7,13 @@ #define GTP0_PORT 3386 #define GTP1U_PORT 2152 +/* GTP messages types */ +#define GTP_ECHO_REQ 1 /* Echo Request */ +#define GTP_ECHO_RSP 2 /* Echo Response */ #define GTP_TPDU 255 +#define GTPIE_RECOVERY 14 + struct gtp0_header { /* According to GSM TS 09.60. */ __u8 flags; __u8 type; @@ -27,6 +32,32 @@ struct gtp1_header { /* According to 3GPP TS 29.060. */ __be32 tid; } __attribute__ ((packed)); +struct gtp1_header_long { /* According to 3GPP TS 29.060. */ + __u8 flags; + __u8 type; + __be16 length; + __be32 tid; + __be16 seq; + __u8 npdu; + __u8 next; +} __packed; + +/* GTP Information Element */ +struct gtp_ie { + __u8 tag; + __u8 val; +} __packed; + +struct gtp0_packet { + struct gtp0_header gtp0_h; + struct gtp_ie ie; +} __packed; + +struct gtp1u_packet { + struct gtp1_header_long gtp1u_h; + struct gtp_ie ie; +} __packed; + #define GTP1_F_NPDU 0x01 #define GTP1_F_SEQ 0x02 #define GTP1_F_EXTHDR 0x04 diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h index 42f3fb097271..0123a8024ef2 100644 --- a/include/uapi/linux/if_link.h +++ b/include/uapi/linux/if_link.h @@ -823,6 +823,7 @@ enum { IFLA_GTP_PDP_HASHSIZE, IFLA_GTP_ROLE, IFLA_GTP_CREATE_SOCKETS, + IFLA_GTP_RESTART_COUNT, __IFLA_GTP_MAX, }; #define IFLA_GTP_MAX (__IFLA_GTP_MAX - 1) -- 2.31.1