ipvs: optimize checksums for apps

 	Avoid full checksum calculation for apps that can provide
info whether csum was broken after payload mangling. For now only
ip_vs_ftp mangles payload and it updates the csum, so the full
recalculation is avoided for all packets.

 	Add CHECKSUM_UNNECESSARY for snat_handler (TCP and UDP).
It is needed to support SNAT from local address for the case
when csum is fully recalculated.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

3 files changed, 56 insertions, 13 deletions

diff --git a/net/netfilter/ipvs/ip_vs_ftp.c b/net/netfilter/ipvs/ip_vs_ftp.c
index 090889a3b3af..75455000ad1c 100644
--- a/net/netfilter/ipvs/ip_vs_ftp.c
+++ b/net/netfilter/ipvs/ip_vs_ftp.c
@@ -242,9 +242,14 @@ static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
                         ret = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
                                                        start-data, end-start,
                                                        buf, buf_len);
-                        if (ret)
+                        if (ret) {
                                 ip_vs_nfct_expect_related(skb, ct, n_cp,
                                                           IPPROTO_TCP, 0, 0);
+                                if (skb->ip_summed == CHECKSUM_COMPLETE)
+                                        skb->ip_summed = CHECKSUM_UNNECESSARY;
+                                /* csum is updated */
+                                ret = 1;
+                        }
                 }
 
                 /*
diff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c b/net/netfilter/ipvs/ip_vs_proto_tcp.c
index 318d011036db..64dc2954cf78 100644
--- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
@@ -120,6 +120,7 @@ tcp_snat_handler(struct sk_buff *skb,
         struct tcphdr *tcph;
         unsigned int tcphoff;
         int oldlen;
+        int payload_csum = 0;
 
 #ifdef CONFIG_IP_VS_IPV6
         if (cp->af == AF_INET6)
@@ -134,13 +135,20 @@ tcp_snat_handler(struct sk_buff *skb,
                 return 0;
 
         if (unlikely(cp->app != NULL)) {
+                int ret;
+
                 /* Some checks before mangling */
                 if (pp->csum_check && !pp->csum_check(cp->af, skb, pp))
                         return 0;
 
                 /* Call application helper if needed */
-                if (!ip_vs_app_pkt_out(cp, skb))
+                if (!(ret = ip_vs_app_pkt_out(cp, skb)))
                         return 0;
+                /* ret=2: csum update is needed after payload mangling */
+                if (ret == 1)
+                        oldlen = skb->len - tcphoff;
+                else
+                        payload_csum = 1;
         }
 
         tcph = (void *)skb_network_header(skb) + tcphoff;
@@ -151,12 +159,13 @@ tcp_snat_handler(struct sk_buff *skb,
                 tcp_partial_csum_update(cp->af, tcph, &cp->daddr, &cp->vaddr,
                                         htons(oldlen),
                                         htons(skb->len - tcphoff));
-        } else if (!cp->app) {
+        } else if (!payload_csum) {
                 /* Only port and addr are changed, do fast csum update */
                 tcp_fast_csum_update(cp->af, tcph, &cp->daddr, &cp->vaddr,
                                      cp->dport, cp->vport);
                 if (skb->ip_summed == CHECKSUM_COMPLETE)
-                        skb->ip_summed = CHECKSUM_NONE;
+                        skb->ip_summed = (cp->app && pp->csum_check) ?
+                                         CHECKSUM_UNNECESSARY : CHECKSUM_NONE;
         } else {
                 /* full checksum calculation */
                 tcph->check = 0;
@@ -174,6 +183,7 @@ tcp_snat_handler(struct sk_buff *skb,
                                                         skb->len - tcphoff,
                                                         cp->protocol,
                                                         skb->csum);
+                skb->ip_summed = CHECKSUM_UNNECESSARY;
 
                 IP_VS_DBG(11, "O-pkt: %s O-csum=%d (+%zd)\n",
                           pp->name, tcph->check,
@@ -190,6 +200,7 @@ tcp_dnat_handler(struct sk_buff *skb,
         struct tcphdr *tcph;
         unsigned int tcphoff;
         int oldlen;
+        int payload_csum = 0;
 
 #ifdef CONFIG_IP_VS_IPV6
         if (cp->af == AF_INET6)
@@ -204,6 +215,8 @@ tcp_dnat_handler(struct sk_buff *skb,
                 return 0;
 
         if (unlikely(cp->app != NULL)) {
+                int ret;
+
                 /* Some checks before mangling */
                 if (pp->csum_check && !pp->csum_check(cp->af, skb, pp))
                         return 0;
@@ -212,8 +225,13 @@ tcp_dnat_handler(struct sk_buff *skb,
                  *      Attempt ip_vs_app call.
                  *      It will fix ip_vs_conn and iph ack_seq stuff
                  */
-                if (!ip_vs_app_pkt_in(cp, skb))
+                if (!(ret = ip_vs_app_pkt_in(cp, skb)))
                         return 0;
+                /* ret=2: csum update is needed after payload mangling */
+                if (ret == 1)
+                        oldlen = skb->len - tcphoff;
+                else
+                        payload_csum = 1;
         }
 
         tcph = (void *)skb_network_header(skb) + tcphoff;
@@ -226,12 +244,13 @@ tcp_dnat_handler(struct sk_buff *skb,
                 tcp_partial_csum_update(cp->af, tcph, &cp->vaddr, &cp->daddr,
                                         htons(oldlen),
                                         htons(skb->len - tcphoff));
-        } else if (!cp->app) {
+        } else if (!payload_csum) {
                 /* Only port and addr are changed, do fast csum update */
                 tcp_fast_csum_update(cp->af, tcph, &cp->vaddr, &cp->daddr,
                                      cp->vport, cp->dport);
                 if (skb->ip_summed == CHECKSUM_COMPLETE)
-                        skb->ip_summed = CHECKSUM_NONE;
+                        skb->ip_summed = (cp->app && pp->csum_check) ?
+                                         CHECKSUM_UNNECESSARY : CHECKSUM_NONE;
         } else {
                 /* full checksum calculation */
                 tcph->check = 0;
diff --git a/net/netfilter/ipvs/ip_vs_proto_udp.c b/net/netfilter/ipvs/ip_vs_proto_udp.c
index f9290893bd93..9c558c40bfbb 100644
--- a/net/netfilter/ipvs/ip_vs_proto_udp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_udp.c
@@ -121,6 +121,7 @@ udp_snat_handler(struct sk_buff *skb,
         struct udphdr *udph;
         unsigned int udphoff;
         int oldlen;
+        int payload_csum = 0;
 
 #ifdef CONFIG_IP_VS_IPV6
         if (cp->af == AF_INET6)
@@ -135,6 +136,8 @@ udp_snat_handler(struct sk_buff *skb,
                 return 0;
 
         if (unlikely(cp->app != NULL)) {
+                int ret;
+
                 /* Some checks before mangling */
                 if (pp->csum_check && !pp->csum_check(cp->af, skb, pp))
                         return 0;
@@ -142,8 +145,13 @@ udp_snat_handler(struct sk_buff *skb,
                 /*
                  *      Call application helper if needed
                  */
-                if (!ip_vs_app_pkt_out(cp, skb))
+                if (!(ret = ip_vs_app_pkt_out(cp, skb)))
                         return 0;
+                /* ret=2: csum update is needed after payload mangling */
+                if (ret == 1)
+                        oldlen = skb->len - udphoff;
+                else
+                        payload_csum = 1;
         }
 
         udph = (void *)skb_network_header(skb) + udphoff;
@@ -156,12 +164,13 @@ udp_snat_handler(struct sk_buff *skb,
                 udp_partial_csum_update(cp->af, udph, &cp->daddr, &cp->vaddr,
                                         htons(oldlen),
                                         htons(skb->len - udphoff));
-        } else if (!cp->app && (udph->check != 0)) {
+        } else if (!payload_csum && (udph->check != 0)) {
                 /* Only port and addr are changed, do fast csum update */
                 udp_fast_csum_update(cp->af, udph, &cp->daddr, &cp->vaddr,
                                      cp->dport, cp->vport);
                 if (skb->ip_summed == CHECKSUM_COMPLETE)
-                        skb->ip_summed = CHECKSUM_NONE;
+                        skb->ip_summed = (cp->app && pp->csum_check) ?
+                                         CHECKSUM_UNNECESSARY : CHECKSUM_NONE;
         } else {
                 /* full checksum calculation */
                 udph->check = 0;
@@ -181,6 +190,7 @@ udp_snat_handler(struct sk_buff *skb,
                                                         skb->csum);
                 if (udph->check == 0)
                         udph->check = CSUM_MANGLED_0;
+                skb->ip_summed = CHECKSUM_UNNECESSARY;
                 IP_VS_DBG(11, "O-pkt: %s O-csum=%d (+%zd)\n",
                           pp->name, udph->check,
                           (char*)&(udph->check) - (char*)udph);
@@ -196,6 +206,7 @@ udp_dnat_handler(struct sk_buff *skb,
         struct udphdr *udph;
         unsigned int udphoff;
         int oldlen;
+        int payload_csum = 0;
 
 #ifdef CONFIG_IP_VS_IPV6
         if (cp->af == AF_INET6)
@@ -210,6 +221,8 @@ udp_dnat_handler(struct sk_buff *skb,
                 return 0;
 
         if (unlikely(cp->app != NULL)) {
+                int ret;
+
                 /* Some checks before mangling */
                 if (pp->csum_check && !pp->csum_check(cp->af, skb, pp))
                         return 0;
@@ -218,8 +231,13 @@ udp_dnat_handler(struct sk_buff *skb,
                  *      Attempt ip_vs_app call.
                  *      It will fix ip_vs_conn
                  */
-                if (!ip_vs_app_pkt_in(cp, skb))
+                if (!(ret = ip_vs_app_pkt_in(cp, skb)))
                         return 0;
+                /* ret=2: csum update is needed after payload mangling */
+                if (ret == 1)
+                        oldlen = skb->len - udphoff;
+                else
+                        payload_csum = 1;
         }
 
         udph = (void *)skb_network_header(skb) + udphoff;
@@ -232,12 +250,13 @@ udp_dnat_handler(struct sk_buff *skb,
                 udp_partial_csum_update(cp->af, udph, &cp->vaddr, &cp->daddr,
                                         htons(oldlen),
                                         htons(skb->len - udphoff));
-        } else if (!cp->app && (udph->check != 0)) {
+        } else if (!payload_csum && (udph->check != 0)) {
                 /* Only port and addr are changed, do fast csum update */
                 udp_fast_csum_update(cp->af, udph, &cp->vaddr, &cp->daddr,
                                      cp->vport, cp->dport);
                 if (skb->ip_summed == CHECKSUM_COMPLETE)
-                        skb->ip_summed = CHECKSUM_NONE;
+                        skb->ip_summed = (cp->app && pp->csum_check) ?
+                                         CHECKSUM_UNNECESSARY : CHECKSUM_NONE;
         } else {
                 /* full checksum calculation */
                 udph->check = 0;