[NET]: Supporting UDP-Lite (RFC 3828) in Linux

This is a revision of the previously submitted patch, which alters
the way files are organized and compiled in the following manner:

	* UDP and UDP-Lite now use separate object files
	* source file dependencies resolved via header files
	  net/ipv{4,6}/udp_impl.h
	* order of inclusion files in udp.c/udplite.c adapted
	  accordingly

[NET/IPv4]: Support for the UDP-Lite protocol (RFC 3828)

This patch adds support for UDP-Lite to the IPv4 stack, provided as an
extension to the existing UDPv4 code:
        * generic routines are all located in net/ipv4/udp.c
        * UDP-Lite specific routines are in net/ipv4/udplite.c
        * MIB/statistics support in /proc/net/snmp and /proc/net/udplite
        * shared API with extensions for partial checksum coverage

[NET/IPv6]: Extension for UDP-Lite over IPv6

It extends the existing UDPv6 code base with support for UDP-Lite
in the same manner as per UDPv4. In particular,
        * UDPv6 generic and shared code is in net/ipv6/udp.c
        * UDP-Litev6 specific extensions are in net/ipv6/udplite.c
        * MIB/statistics support in /proc/net/snmp6 and /proc/net/udplite6
        * support for IPV6_ADDRFORM
        * aligned the coding style of protocol initialisation with af_inet6.c
        * made the error handling in udpv6_queue_rcv_skb consistent;
          to return `-1' on error on all error cases
        * consolidation of shared code

[NET]: UDP-Lite Documentation and basic XFRM/Netfilter support

The UDP-Lite patch further provides
        * API documentation for UDP-Lite
        * basic xfrm support
        * basic netfilter support for IPv4 and IPv6 (LOG target)

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 149 insertions, 0 deletions

diff --git a/include/net/udplite.h b/include/net/udplite.h
new file mode 100644
index 000000000000..1473b3e49044
--- /dev/null
+++ b/include/net/udplite.h
@@ -0,0 +1,149 @@
+/*
+ *      Definitions for the UDP-Lite (RFC 3828) code.
+ */
+#ifndef _UDPLITE_H
+#define _UDPLITE_H
+
+/* UDP-Lite socket options */
+#define UDPLITE_SEND_CSCOV   10 /* sender partial coverage (as sent)      */
+#define UDPLITE_RECV_CSCOV   11 /* receiver partial coverage (threshold ) */
+
+extern struct proto             udplite_prot;
+extern struct hlist_head        udplite_hash[UDP_HTABLE_SIZE];
+
+/* UDP-Lite does not have a standardized MIB yet, so we inherit from UDP */
+DECLARE_SNMP_STAT(struct udp_mib, udplite_statistics);
+
+/*
+ *      Checksum computation is all in software, hence simpler getfrag.
+ */
+static __inline__ int udplite_getfrag(void *from, char *to, int  offset,
+                                      int len, int odd, struct sk_buff *skb)
+{
+        return memcpy_fromiovecend(to, (struct iovec *) from, offset, len);
+}
+
+/* Designate sk as UDP-Lite socket */
+static inline int udplite_sk_init(struct sock *sk)
+{
+        udp_sk(sk)->pcflag = UDPLITE_BIT;
+        return 0;
+}
+
+/*
+ *      Checksumming routines
+ */
+static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
+{
+        u16 cscov;
+
+        /* In UDPv4 a zero checksum means that the transmitter generated no
+         * checksum. UDP-Lite (like IPv6) mandates checksums, hence packets
+         * with a zero checksum field are illegal.                            */
+        if (uh->check == 0) {
+                LIMIT_NETDEBUG(KERN_DEBUG "UDPLITE: zeroed checksum field\n");
+                return 1;
+        }
+
+        UDP_SKB_CB(skb)->partial_cov = 0;
+        cscov = ntohs(uh->len);
+
+        if (cscov == 0)          /* Indicates that full coverage is required. */
+                cscov = skb->len;
+        else if (cscov < 8  || cscov > skb->len) {
+                /*
+                 * Coverage length violates RFC 3828: log and discard silently.
+                 */
+                LIMIT_NETDEBUG(KERN_DEBUG "UDPLITE: bad csum coverage %d/%d\n",
+                               cscov, skb->len);
+                return 1;
+
+        } else if (cscov < skb->len)
+                UDP_SKB_CB(skb)->partial_cov = 1;
+
+        UDP_SKB_CB(skb)->cscov = cscov;
+
+        /*
+         * There is no known NIC manufacturer supporting UDP-Lite yet,
+         * hence ip_summed is always (re-)set to CHECKSUM_NONE.
+         */
+        skb->ip_summed = CHECKSUM_NONE;
+
+        return 0;
+}
+
+static __inline__ int udplite4_csum_init(struct sk_buff *skb, struct udphdr *uh)
+{
+        int rc = udplite_checksum_init(skb, uh);
+
+        if (!rc)
+                skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr,
+                                               skb->nh.iph->daddr,
+                                               skb->len, IPPROTO_UDPLITE, 0);
+        return rc;
+}
+
+static __inline__ int udplite6_csum_init(struct sk_buff *skb, struct udphdr *uh)
+{
+        int rc = udplite_checksum_init(skb, uh);
+
+        if (!rc)
+                skb->csum = ~csum_ipv6_magic(&skb->nh.ipv6h->saddr,
+                                             &skb->nh.ipv6h->daddr,
+                                             skb->len, IPPROTO_UDPLITE, 0);
+        return rc;
+}
+
+static inline int udplite_sender_cscov(struct udp_sock *up, struct udphdr *uh)
+{
+        int cscov = up->len;
+
+        /*
+         * Sender has set `partial coverage' option on UDP-Lite socket
+         */
+        if (up->pcflag & UDPLITE_SEND_CC)    {
+                if (up->pcslen < up->len) {
+                /* up->pcslen == 0 means that full coverage is required,
+                 * partial coverage only if  0 < up->pcslen < up->len */
+                        if (0 < up->pcslen) {
+                               cscov = up->pcslen;
+                        }
+                        uh->len = htons(up->pcslen);
+                }
+        /*
+         * NOTE: Causes for the error case  `up->pcslen > up->len':
+         *        (i)  Application error (will not be penalized).
+         *       (ii)  Payload too big for send buffer: data is split
+         *             into several packets, each with its own header.
+         *             In this case (e.g. last segment), coverage may
+         *             exceed packet length.
+         *       Since packets with coverage length > packet length are
+         *       illegal, we fall back to the defaults here.
+         */
+        }
+        return cscov;
+}
+
+static inline u32 udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)
+{
+        u32 csum = 0;
+        int off, len, cscov = udplite_sender_cscov(udp_sk(sk), skb->h.uh);
+
+        skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
+
+        skb_queue_walk(&sk->sk_write_queue, skb) {
+                off = skb->h.raw - skb->data;
+                len = skb->len - off;
+
+                csum = skb_checksum(skb, off, (cscov > len)? len : cscov, csum);
+
+                if ((cscov -= len) <= 0)
+                        break;
+        }
+        return csum;
+}
+
+extern void     udplite4_register(void);
+extern int      udplite_get_port(struct sock *sk, unsigned short snum,
+                        int (*scmp)(const struct sock *, const struct sock *));
+#endif  /* _UDPLITE_H */