Merge branch 'inet_csums_part2'

Tom Herbert says:

====================
net: Checksum offload changes - Part II

I am working on overhauling RX checksum offload. Goals of this effort
are:

- Specify what exactly it means when driver returns CHECKSUM_UNNECESSARY
- Preserve CHECKSUM_COMPLETE through encapsulation layers
- Don't do skb_checksum more than once per packet
- Unify GRO and non-GRO csum verification as much as possible
- Unify the checksum functions (checksum_init)
- Simply code

What is in this second patch set:

- Call common inet checksum validation functions in ICMP{4,6},
  GRE{4,6}, and IGMP.
- In UDP, verify checksum before handing off to encap_rcv.
- Remove custom UDP checksum validation code in L2TP.

Please review carefully and test if possible, mucking with basic
checksum functions is always a little precarious :-)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 20 insertions, 126 deletions

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index 250be7421ab3..fbfd829f4049 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -93,28 +93,6 @@ void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
 }
 EXPORT_SYMBOL_GPL(gre_build_header);
 
-static __sum16 check_checksum(struct sk_buff *skb)
-{
-        __sum16 csum = 0;
-
-        switch (skb->ip_summed) {
-        case CHECKSUM_COMPLETE:
-                csum = csum_fold(skb->csum);
-
-                if (!csum)
-                        break;
-                /* Fall through. */
-
-        case CHECKSUM_NONE:
-                skb->csum = 0;
-                csum = __skb_checksum_complete(skb);
-                skb->ip_summed = CHECKSUM_COMPLETE;
-                break;
-        }
-
-        return csum;
-}
-
 static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
                             bool *csum_err)
 {
@@ -141,7 +119,7 @@ static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
 
         options = (__be32 *)(greh + 1);
         if (greh->flags & GRE_CSUM) {
-                if (check_checksum(skb)) {
+                if (skb_checksum_simple_validate(skb)) {
                         *csum_err = true;
                         return -EINVAL;
                 }
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 0134663fdbce..fe52666dc43c 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -908,16 +908,8 @@ int icmp_rcv(struct sk_buff *skb)
 
         ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS);
 
-        switch (skb->ip_summed) {
-        case CHECKSUM_COMPLETE:
-                if (!csum_fold(skb->csum))
-                        break;
-                /* fall through */
-        case CHECKSUM_NONE:
-                skb->csum = 0;
-                if (__skb_checksum_complete(skb))
-                        goto csum_error;
-        }
+        if (skb_checksum_simple_validate(skb))
+                goto csum_error;
 
         if (!pskb_pull(skb, sizeof(*icmph)))
                 goto error;
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 97e4d1655d26..17d34e3c2ac3 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -988,16 +988,8 @@ int igmp_rcv(struct sk_buff *skb)
         if (!pskb_may_pull(skb, sizeof(struct igmphdr)))
                 goto drop;
 
-        switch (skb->ip_summed) {
-        case CHECKSUM_COMPLETE:
-                if (!csum_fold(skb->csum))
-                        break;
-                /* fall through */
-        case CHECKSUM_NONE:
-                skb->csum = 0;
-                if (__skb_checksum_complete(skb))
-                        goto drop;
-        }
+        if (skb_checksum_simple_validate(skb))
+                goto drop;
 
         ih = igmp_hdr(skb);
         switch (ih->type) {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index f2d05d7be743..54ea0a3a48f1 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1495,6 +1495,10 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
                 if (skb->len > sizeof(struct udphdr) && encap_rcv != NULL) {
                         int ret;
 
+                        /* Verify checksum before giving to encap */
+                        if (udp_lib_checksum_complete(skb))
+                                goto csum_error;
+
                         ret = encap_rcv(sk, skb);
                         if (ret <= 0) {
                                 UDP_INC_STATS_BH(sock_net(sk),
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 3b0905b77127..8d3952796d39 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -692,22 +692,11 @@ static int icmpv6_rcv(struct sk_buff *skb)
         saddr = &ipv6_hdr(skb)->saddr;
         daddr = &ipv6_hdr(skb)->daddr;
 
-        /* Perform checksum. */
-        switch (skb->ip_summed) {
-        case CHECKSUM_COMPLETE:
-                if (!csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_ICMPV6,
-                                     skb->csum))
-                        break;
-                /* fall through */
-        case CHECKSUM_NONE:
-                skb->csum = ~csum_unfold(csum_ipv6_magic(saddr, daddr, skb->len,
-                                             IPPROTO_ICMPV6, 0));
-                if (__skb_checksum_complete(skb)) {
-                        LIMIT_NETDEBUG(KERN_DEBUG
-                                       "ICMPv6 checksum failed [%pI6c > %pI6c]\n",
-                                       saddr, daddr);
-                        goto csum_error;
-                }
+        if (skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo)) {
+                LIMIT_NETDEBUG(KERN_DEBUG
+                               "ICMPv6 checksum failed [%pI6c > %pI6c]\n",
+                               saddr, daddr);
+                goto csum_error;
         }
 
         if (!pskb_pull(skb, sizeof(*hdr)))
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 75277b739b04..3873181ed856 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -468,17 +468,7 @@ static int ip6gre_rcv(struct sk_buff *skb)
                         goto drop;
 
                 if (flags&GRE_CSUM) {
-                        switch (skb->ip_summed) {
-                        case CHECKSUM_COMPLETE:
-                                csum = csum_fold(skb->csum);
-                                if (!csum)
-                                        break;
-                                /* fall through */
-                        case CHECKSUM_NONE:
-                                skb->csum = 0;
-                                csum = __skb_checksum_complete(skb);
-                                skb->ip_summed = CHECKSUM_COMPLETE;
-                        }
+                        csum = skb_checksum_simple_validate(skb);
                         offset += 4;
                 }
                 if (flags&GRE_KEY) {
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index fc2be63e32d5..7edf096867c4 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -634,6 +634,10 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
                 if (skb->len > sizeof(struct udphdr) && encap_rcv != NULL) {
                         int ret;
 
+                        /* Verify checksum before giving to encap */
+                        if (udp_lib_checksum_complete(skb))
+                                goto csum_error;
+
                         ret = encap_rcv(sk, skb);
                         if (ret <= 0) {
                                 UDP_INC_STATS_BH(sock_net(sk),
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index a4e37d7158dc..aa1a9d44c107 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -495,52 +495,6 @@ out:
         spin_unlock_bh(&session->reorder_q.lock);
 }
 
-static inline int l2tp_verify_udp_checksum(struct sock *sk,
-                                           struct sk_buff *skb)
-{
-        struct udphdr *uh = udp_hdr(skb);
-        u16 ulen = ntohs(uh->len);
-        __wsum psum;
-
-        if (sk->sk_no_check || skb_csum_unnecessary(skb))
-                return 0;
-
-#if IS_ENABLED(CONFIG_IPV6)
-        if (sk->sk_family == PF_INET6 && !l2tp_tunnel(sk)->v4mapped) {
-                if (!uh->check) {
-                        LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
-                        return 1;
-                }
-                if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
-                    !csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
-                                     &ipv6_hdr(skb)->daddr, ulen,
-                                     IPPROTO_UDP, skb->csum)) {
-                        skb->ip_summed = CHECKSUM_UNNECESSARY;
-                        return 0;
-                }
-                skb->csum = ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
-                                                         &ipv6_hdr(skb)->daddr,
-                                                         skb->len, IPPROTO_UDP,
-                                                         0));
-        } else
-#endif
-        {
-                struct inet_sock *inet;
-                if (!uh->check)
-                        return 0;
-                inet = inet_sk(sk);
-                psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr,
-                                          ulen, IPPROTO_UDP, 0);
-
-                if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
-                    !csum_fold(csum_add(psum, skb->csum)))
-                        return 0;
-                skb->csum = psum;
-        }
-
-        return __skb_checksum_complete(skb);
-}
-
 static int l2tp_seq_check_rx_window(struct l2tp_session *session, u32 nr)
 {
         u32 nws;
@@ -895,8 +849,7 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
         u16 version;
         int length;
 
-        if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
-                goto discard_bad_csum;
+        /* UDP has verifed checksum */
 
         /* UDP always verifies the packet length. */
         __skb_pull(skb, sizeof(struct udphdr));
@@ -979,14 +932,6 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 
         return 0;
 
-discard_bad_csum:
-        LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
-        UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
-        atomic_long_inc(&tunnel->stats.rx_errors);
-        kfree_skb(skb);
-
-        return 0;
-
 error:
         /* Put UDP header back */
         __skb_push(skb, sizeof(struct udphdr));