The GTP-tunnel driver is explicitly GGSN-side as it searches for PDP contexts based on the incoming packets _destination_ address. If we want to place ourselves on the SGSN side of the tunnel, then we want to be identifying PDP contexts based on _source_ address.
Let it be noted that in a "real" configuration this module would never be used: the SGSN normally does not see IP packets as input. The justification for this functionality is for PGW load-testing applications where the input to the SGSN is locally generally IP traffic. This patch adds a "role" argument at GTP-link creation time to specify whether we are on the GGSN or SGSN side of the tunnel; this flag is then used to determine which part of the IP packet to use in determining the PDP context. Signed-off-by: Jonas Bonn <jo...@southpole.se> Acked-by: Pablo Neira Ayuso <pa...@netfilter.org> --- drivers/net/gtp.c | 41 +++++++++++++++++++++++++++++++---------- include/uapi/linux/if_link.h | 7 +++++++ 2 files changed, 38 insertions(+), 10 deletions(-) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 3806be6..b54d1a3 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -72,6 +72,7 @@ struct gtp_dev { struct net *net; struct net_device *dev; + unsigned int role; unsigned int hash_size; struct hlist_head *tid_hash; struct hlist_head *addr_hash; @@ -150,8 +151,8 @@ static struct pdp_ctx *ipv4_pdp_find(struct gtp_dev *gtp, __be32 ms_addr) return NULL; } -static bool gtp_check_src_ms_ipv4(struct sk_buff *skb, struct pdp_ctx *pctx, - unsigned int hdrlen) +static bool gtp_check_ms_ipv4(struct sk_buff *skb, struct pdp_ctx *pctx, + unsigned int hdrlen, unsigned int role) { struct iphdr *iph; @@ -160,18 +161,22 @@ static bool gtp_check_src_ms_ipv4(struct sk_buff *skb, struct pdp_ctx *pctx, iph = (struct iphdr *)(skb->data + hdrlen); - return iph->saddr == pctx->ms_addr_ip4.s_addr; + if (role == GTP_ROLE_SGSN) { + return iph->daddr == pctx->ms_addr_ip4.s_addr; + } else { + return iph->saddr == pctx->ms_addr_ip4.s_addr; + } } -/* Check if the inner IP source address in this packet is assigned to any +/* Check if the inner IP address in this packet is assigned to any * existing mobile subscriber. */ -static bool gtp_check_src_ms(struct sk_buff *skb, struct pdp_ctx *pctx, - unsigned int hdrlen) +static bool gtp_check_ms(struct sk_buff *skb, struct pdp_ctx *pctx, + unsigned int hdrlen, unsigned int role) { switch (ntohs(skb->protocol)) { case ETH_P_IP: - return gtp_check_src_ms_ipv4(skb, pctx, hdrlen); + return gtp_check_ms_ipv4(skb, pctx, hdrlen, role); } return false; } @@ -205,7 +210,7 @@ static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb, goto out_rcu; } - if (!gtp_check_src_ms(skb, pctx, hdrlen)) { + if (!gtp_check_ms(skb, pctx, hdrlen, gtp->role)) { netdev_dbg(gtp->dev, "No PDP ctx for this MS\n"); ret = -1; goto out_rcu; @@ -262,7 +267,7 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb, goto out_rcu; } - if (!gtp_check_src_ms(skb, pctx, hdrlen)) { + if (!gtp_check_ms(skb, pctx, hdrlen, gtp->role)) { netdev_dbg(gtp->dev, "No PDP ctx for this MS\n"); ret = -1; goto out_rcu; @@ -491,7 +496,11 @@ static int gtp_build_skb_ip4(struct sk_buff *skb, struct net_device *dev, * Prepend PDP header with TEI/TID from PDP ctx. */ iph = ip_hdr(skb); - pctx = ipv4_pdp_find(gtp, iph->daddr); + if (gtp->role == GTP_ROLE_SGSN) { + pctx = ipv4_pdp_find(gtp, iph->saddr); + } else { + pctx = ipv4_pdp_find(gtp, iph->daddr); + } if (!pctx) { netdev_dbg(dev, "no PDP ctx found for %pI4, skip\n", &iph->daddr); @@ -666,12 +675,23 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev, int hashsize, err, fd0, fd1; struct gtp_dev *gtp; struct gtp_net *gn; + unsigned int role; + + if (data[IFLA_GTP_ROLE]) { + role = nla_get_u32(data[IFLA_GTP_ROLE]); + if (role > GTP_ROLE_SGSN) + return -EINVAL; + } else { + role = GTP_ROLE_GGSN; + } if (!data[IFLA_GTP_FD0] || !data[IFLA_GTP_FD1]) return -EINVAL; gtp = netdev_priv(dev); + gtp->role = role; + fd0 = nla_get_u32(data[IFLA_GTP_FD0]); fd1 = nla_get_u32(data[IFLA_GTP_FD1]); @@ -723,6 +743,7 @@ static const struct nla_policy gtp_policy[IFLA_GTP_MAX + 1] = { [IFLA_GTP_FD0] = { .type = NLA_U32 }, [IFLA_GTP_FD1] = { .type = NLA_U32 }, [IFLA_GTP_PDP_HASHSIZE] = { .type = NLA_U32 }, + [IFLA_GTP_ROLE] = { .type = NLA_U32 }, }; static int gtp_validate(struct nlattr *tb[], struct nlattr *data[]) diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h index ccde456..da62d8c 100644 --- a/include/uapi/linux/if_link.h +++ b/include/uapi/linux/if_link.h @@ -533,11 +533,18 @@ enum { #define IFLA_PPP_MAX (__IFLA_PPP_MAX - 1) /* GTP section */ + +enum ifla_gtp_role { + GTP_ROLE_GGSN = 0, + GTP_ROLE_SGSN, +}; + enum { IFLA_GTP_UNSPEC, IFLA_GTP_FD0, IFLA_GTP_FD1, IFLA_GTP_PDP_HASHSIZE, + IFLA_GTP_ROLE, __IFLA_GTP_MAX, }; #define IFLA_GTP_MAX (__IFLA_GTP_MAX - 1) -- 2.9.3