Merge branch 'ip_cmsg_csum'

Tom Herbert says:

====================
ip: Support checksum returned in csmg

This patch set allows the packet checksum for a datagram socket
to be returned in csum data in recvmsg. This allows userspace
to implement its own checksum over the data, for instance if an
IP tunnel was be implemented in user space, the inner checksum
could be validated.

Changes in this patch set:
  - Move checksum conversion to inet_sock from udp_sock. This
    generalizes checksum conversion for use with other protocols.
  - Move IP cmsg constants to a header file and make processing
    of the flags more efficient in ip_cmsg_recv
  - Return checksum value in cmsg. This is specifically the unfolded
    32 bit checksum of the full packet starting from the first byte
    returned in recvmsg

Tested: Wrote a little server to get checksums in cmsg for UDP and
        verfied correct checksum is returned.
====================

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

5 files changed, 84 insertions, 34 deletions

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index b986298a7ba3..2197c36f722f 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -490,7 +490,7 @@ static int fou_create(struct net *net, struct fou_cfg *cfg,
 	sk->sk_user_data = fou;
 	fou->sock = sock;
 
-	udp_set_convert_csum(sk, true);
+	inet_inc_convert_csum(sk);
 
 	sk->sk_allocation = GFP_ATOMIC;
 
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 8a89c738b7a3..a317797b3cd0 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -37,6 +37,7 @@
 #include <net/route.h>
 #include <net/xfrm.h>
 #include <net/compat.h>
+#include <net/checksum.h>
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/transp_v6.h>
 #endif
@@ -45,14 +46,6 @@
 #include <linux/errqueue.h>
 #include <asm/uaccess.h>
 
-#define IP_CMSG_PKTINFO		1
-#define IP_CMSG_TTL		2
-#define IP_CMSG_TOS		4
-#define IP_CMSG_RECVOPTS	8
-#define IP_CMSG_RETOPTS		16
-#define IP_CMSG_PASSSEC		32
-#define IP_CMSG_ORIGDSTADDR     64
-
 /*
  *	SOL_IP control messages.
  */
@@ -104,6 +97,20 @@ static void ip_cmsg_recv_retopts(struct msghdr *msg, struct sk_buff *skb)
 	put_cmsg(msg, SOL_IP, IP_RETOPTS, opt->optlen, opt->__data);
 }
 
+static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,
+				  int offset)
+{
+	__wsum csum = skb->csum;
+
+	if (skb->ip_summed != CHECKSUM_COMPLETE)
+		return;
+
+	if (offset != 0)
+		csum = csum_sub(csum, csum_partial(skb->data, offset, 0));
+
+	put_cmsg(msg, SOL_IP, IP_CHECKSUM, sizeof(__wsum), &csum);
+}
+
 static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
 {
 	char *secdata;
@@ -144,47 +151,73 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
 	put_cmsg(msg, SOL_IP, IP_ORIGDSTADDR, sizeof(sin), &sin);
 }
 
-void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
+			 int offset)
 {
 	struct inet_sock *inet = inet_sk(skb->sk);
 	unsigned int flags = inet->cmsg_flags;
 
 	/* Ordered by supposed usage frequency */
-	if (flags & 1)
+	if (flags & IP_CMSG_PKTINFO) {
 		ip_cmsg_recv_pktinfo(msg, skb);
-	if ((flags >>= 1) == 0)
-		return;
 
-	if (flags & 1)
+		flags &= ~IP_CMSG_PKTINFO;
+		if (!flags)
+			return;
+	}
+
+	if (flags & IP_CMSG_TTL) {
 		ip_cmsg_recv_ttl(msg, skb);
-	if ((flags >>= 1) == 0)
-		return;
 
-	if (flags & 1)
+		flags &= ~IP_CMSG_TTL;
+		if (!flags)
+			return;
+	}
+
+	if (flags & IP_CMSG_TOS) {
 		ip_cmsg_recv_tos(msg, skb);
-	if ((flags >>= 1) == 0)
-		return;
 
-	if (flags & 1)
+		flags &= ~IP_CMSG_TOS;
+		if (!flags)
+			return;
+	}
+
+	if (flags & IP_CMSG_RECVOPTS) {
 		ip_cmsg_recv_opts(msg, skb);
-	if ((flags >>= 1) == 0)
-		return;
 
-	if (flags & 1)
+		flags &= ~IP_CMSG_RECVOPTS;
+		if (!flags)
+			return;
+	}
+
+	if (flags & IP_CMSG_RETOPTS) {
 		ip_cmsg_recv_retopts(msg, skb);
-	if ((flags >>= 1) == 0)
-		return;
 
-	if (flags & 1)
+		flags &= ~IP_CMSG_RETOPTS;
+		if (!flags)
+			return;
+	}
+
+	if (flags & IP_CMSG_PASSSEC) {
 		ip_cmsg_recv_security(msg, skb);
 
-	if ((flags >>= 1) == 0)
-		return;
-	if (flags & 1)
+		flags &= ~IP_CMSG_PASSSEC;
+		if (!flags)
+			return;
+	}
+
+	if (flags & IP_CMSG_ORIGDSTADDR) {
 		ip_cmsg_recv_dstaddr(msg, skb);
 
+		flags &= ~IP_CMSG_ORIGDSTADDR;
+		if (!flags)
+			return;
+	}
+
+	if (flags & IP_CMSG_CHECKSUM)
+		ip_cmsg_recv_checksum(msg, skb, offset);
 }
-EXPORT_SYMBOL(ip_cmsg_recv);
+EXPORT_SYMBOL(ip_cmsg_recv_offset);
 
 int ip_cmsg_send(struct net *net, struct msghdr *msg, struct ipcm_cookie *ipc,
 		 bool allow_ipv6)
@@ -522,6 +555,7 @@ static int do_ip_setsockopt(struct sock *sk, int level,
 	case IP_MULTICAST_ALL:
 	case IP_MULTICAST_LOOP:
 	case IP_RECVORIGDSTADDR:
+	case IP_CHECKSUM:
 		if (optlen >= sizeof(int)) {
 			if (get_user(val, (int __user *) optval))
 				return -EFAULT;
@@ -619,6 +653,19 @@ static int do_ip_setsockopt(struct sock *sk, int level,
 		else
 			inet->cmsg_flags &= ~IP_CMSG_ORIGDSTADDR;
 		break;
+	case IP_CHECKSUM:
+		if (val) {
+			if (!(inet->cmsg_flags & IP_CMSG_CHECKSUM)) {
+				inet_inc_convert_csum(sk);
+				inet->cmsg_flags |= IP_CMSG_CHECKSUM;
+			}
+		} else {
+			if (inet->cmsg_flags & IP_CMSG_CHECKSUM) {
+				inet_dec_convert_csum(sk);
+				inet->cmsg_flags &= ~IP_CMSG_CHECKSUM;
+			}
+		}
+		break;
 	case IP_TOS:	/* This sets both TOS and Precedence */
 		if (sk->sk_type == SOCK_STREAM) {
 			val &= ~INET_ECN_MASK;
@@ -1222,6 +1269,9 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
 	case IP_RECVORIGDSTADDR:
 		val = (inet->cmsg_flags & IP_CMSG_ORIGDSTADDR) != 0;
 		break;
+	case IP_CHECKSUM:
+		val = (inet->cmsg_flags & IP_CMSG_CHECKSUM) != 0;
+		break;
 	case IP_TOS:
 		val = inet->tos;
 		break;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 13b4dcf86ef6..97ef1f8b7be8 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1329,7 +1329,7 @@ try_again:
 		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
-		ip_cmsg_recv(msg, skb);
+		ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr));
 
 	err = copied;
 	if (flags & MSG_TRUNC)
@@ -1806,7 +1806,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	if (sk != NULL) {
 		int ret;
 
-		if (udp_sk(sk)->convert_csum && uh->check && !IS_UDPLITE(sk))
+		if (inet_get_convert_csum(sk) && uh->check && !IS_UDPLITE(sk))
 			skb_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
 						 inet_compute_pseudo);
 
diff --git a/net/ipv4/udp_tunnel.c b/net/ipv4/udp_tunnel.c
index 1671263e5fa0..9996e63ed304 100644
--- a/net/ipv4/udp_tunnel.c
+++ b/net/ipv4/udp_tunnel.c
@@ -63,7 +63,7 @@ void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
 	inet_sk(sk)->mc_loop = 0;
 
 	/* Enable CHECKSUM_UNNECESSARY to CHECKSUM_COMPLETE conversion */
-	udp_set_convert_csum(sk, true);
+	inet_inc_convert_csum(sk);
 
 	rcu_assign_sk_user_data(sk, cfg->sk_user_data);
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 189dc4ae3eca..e41f017cd479 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -909,7 +909,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 			goto csum_error;
 		}
 
-		if (udp_sk(sk)->convert_csum && uh->check && !IS_UDPLITE(sk))
+		if (inet_get_convert_csum(sk) && uh->check && !IS_UDPLITE(sk))
 			skb_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
 						 ip6_compute_pseudo);