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[PATCH] ipvs: allow tunneling with gre encapsulation

To: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Subject: [PATCH] ipvs: allow tunneling with gre encapsulation
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>, Wensong Zhang <wensong@xxxxxxxxxxxx>, Julian Anastasov <ja@xxxxxx>, Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>, Florian Westphal <fw@xxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx
From: Vadim Fedorenko <vfedorenko@xxxxxxxxxxxxxx>
Date: Tue, 25 Jun 2019 18:59:54 +0300
windows real servers can handle gre tunnels, this patch allows
gre encapsulation with the tunneling method, thereby letting ipvs
be load balancer for windows-based services

Signed-off-by: Vadim Fedorenko <vfedorenko@xxxxxxxxxxxxxx>
---
 include/uapi/linux/ip_vs.h      |  1 +
 net/netfilter/ipvs/ip_vs_xmit.c | 76 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+)

diff --git a/include/uapi/linux/ip_vs.h b/include/uapi/linux/ip_vs.h
index e4f1806..4102ddc 100644
--- a/include/uapi/linux/ip_vs.h
+++ b/include/uapi/linux/ip_vs.h
@@ -128,6 +128,7 @@
 enum {
        IP_VS_CONN_F_TUNNEL_TYPE_IPIP = 0,      /* IPIP */
        IP_VS_CONN_F_TUNNEL_TYPE_GUE,           /* GUE */
+       IP_VS_CONN_F_TUNNEL_TYPE_GRE,           /* GRE */
        IP_VS_CONN_F_TUNNEL_TYPE_MAX,
 };

diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
index 71fc6d6..fad3f33 100644
--- a/net/netfilter/ipvs/ip_vs_xmit.c
+++ b/net/netfilter/ipvs/ip_vs_xmit.c
@@ -29,6 +29,7 @@
 #include <linux/tcp.h>                  /* for tcphdr */
 #include <net/ip.h>
 #include <net/gue.h>
+#include <net/gre.h>
 #include <net/tcp.h>                    /* for csum_tcpudp_magic */
 #include <net/udp.h>
 #include <net/icmp.h>                   /* for icmp_send */
@@ -389,6 +390,12 @@ static inline bool decrement_ttl(struct netns_ipvs *ipvs,
                            skb->ip_summed == CHECKSUM_PARTIAL)
                                mtu -= GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
                }
+               if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+                       __be16 tflags = 0;
+                       if (dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
+                               tflags |= TUNNEL_CSUM;
+                       mtu -= gre_calc_hlen(tflags);
+               }
                if (mtu < 68) {
                        IP_VS_DBG_RL("%s(): mtu less than 68\n", __func__);
                        goto err_put;
@@ -549,6 +556,12 @@ static inline bool decrement_ttl(struct netns_ipvs *ipvs,
                            skb->ip_summed == CHECKSUM_PARTIAL)
                                mtu -= GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
                }
+               if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+                       __be16 tflags = 0;
+                       if (dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
+                               tflags |= TUNNEL_CSUM;
+                       mtu -= gre_calc_hlen(tflags);
+               }
                if (mtu < IPV6_MIN_MTU) {
                        IP_VS_DBG_RL("%s(): mtu less than %d\n", __func__,
                                     IPV6_MIN_MTU);
@@ -1079,6 +1092,24 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
        return 0;
 }

+static void
+ipvs_gre_encap(struct net *net, struct sk_buff *skb,
+              struct ip_vs_conn *cp, __u8 *next_protocol)
+{
+       size_t hdrlen;
+       __be16 tflags = 0;
+ __be16 proto = *next_protocol == IPPROTO_IPIP ? htons(ETH_P_IP) : htons(ETH_P_IPV6);
+
+       if (cp->dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
+               tflags |= TUNNEL_CSUM;
+
+       hdrlen = gre_calc_hlen(tflags);
+
+       gre_build_header(skb, hdrlen, tflags, proto, 0, 0);
+
+       *next_protocol = IPPROTO_GRE;
+}
+
 /*
  *   IP Tunneling transmitter
  *
@@ -1153,6 +1184,18 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
                max_headroom += sizeof(struct udphdr) + gue_hdrlen;
        }

+       if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+               size_t gre_hdrlen;
+               __be16 tflags = 0;
+
+               if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
+                       tflags |= TUNNEL_CSUM;
+
+               gre_hdrlen = gre_calc_hlen(tflags);
+
+               max_headroom += gre_hdrlen;
+       }
+
        /* We only care about the df field if sysctl_pmtu_disc(ipvs) is set */
        dfp = sysctl_pmtu_disc(ipvs) ? &df : NULL;
        skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
@@ -1174,6 +1217,13 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
                }
        }

+       if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+               if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
+                       gso_type |= SKB_GSO_GRE_CSUM;
+               else
+                       gso_type |= SKB_GSO_GRE;
+       }
+
        if (iptunnel_handle_offloads(skb, gso_type))
                goto tx_error;

@@ -1194,6 +1244,9 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
                udp_set_csum(!check, skb, saddr, cp->daddr.ip, skb->len);
        }

+       if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+               ipvs_gre_encap(net, skb, cp, &next_protocol);
+       }

        skb_push(skb, sizeof(struct iphdr));
        skb_reset_network_header(skb);
@@ -1289,6 +1342,18 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
                max_headroom += sizeof(struct udphdr) + gue_hdrlen;
        }

+       if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+               size_t gre_hdrlen;
+               __be16 tflags = 0;
+
+               if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
+                       tflags |= TUNNEL_CSUM;
+
+               gre_hdrlen = gre_calc_hlen(tflags);
+
+               max_headroom += gre_hdrlen;
+       }
+
        skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
                                         &next_protocol, &payload_len,
                                         &dsfield, &ttl, NULL);
@@ -1308,6 +1373,13 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
                }
        }

+       if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+               if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
+                       gso_type |= SKB_GSO_GRE_CSUM;
+               else
+                       gso_type |= SKB_GSO_GRE;
+       }
+
        if (iptunnel_handle_offloads(skb, gso_type))
                goto tx_error;

@@ -1328,6 +1400,10 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
                udp6_set_csum(!check, skb, &saddr, &cp->daddr.in6, skb->len);
        }

+       if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
+               ipvs_gre_encap(net, skb, cp, &next_protocol);
+       }
+
        skb_push(skb, sizeof(struct ipv6hdr));
        skb_reset_network_header(skb);
        memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
--
1.9.1

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