packet: support extensible, 64 bit clean mmaped ring structure

The tpacket_hdr is not 64 bit clean due to use of an unsigned long
and can't be extended because the following struct sockaddr_ll needs
to be at a fixed offset.

Add support for a version 2 tpacket protocol that removes these
limitations.

Userspace can query the header size through a new getsockopt option
and change the protocol version through a setsockopt option. The
changes needed to switch to the new protocol version are:

1. replace struct tpacket_hdr by struct tpacket2_hdr
2. query header len and save
3. set protocol version to 2
 - set up ring as usual
4. for getting the sockaddr_ll, use (void *)hdr + TPACKET_ALIGN(hdrlen)
   instead of (void *)hdr + TPACKET_ALIGN(sizeof(struct tpacket_hdr))

Steps 2 and 4 can be omitted if the struct sockaddr_ll isn't needed.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 167 insertions, 33 deletions

diff --git a/include/linux/if_packet.h b/include/linux/if_packet.h
index ad09609227ff..d4d3c82448f5 100644
--- a/include/linux/if_packet.h
+++ b/include/linux/if_packet.h
@@ -43,6 +43,8 @@ struct sockaddr_ll
 #define PACKET_COPY_THRESH              7
 #define PACKET_AUXDATA                  8
 #define PACKET_ORIGDEV                  9
+#define PACKET_VERSION                  10
+#define PACKET_HDRLEN                   11
 
 struct tpacket_stats
 {
@@ -79,6 +81,25 @@ struct tpacket_hdr
 #define TPACKET_ALIGN(x)        (((x)+TPACKET_ALIGNMENT-1)&~(TPACKET_ALIGNMENT-1))
 #define TPACKET_HDRLEN          (TPACKET_ALIGN(sizeof(struct tpacket_hdr)) + sizeof(struct sockaddr_ll))
 
+struct tpacket2_hdr
+{
+        __u32           tp_status;
+        __u32           tp_len;
+        __u32           tp_snaplen;
+        __u16           tp_mac;
+        __u16           tp_net;
+        __u32           tp_sec;
+        __u32           tp_nsec;
+};
+
+#define TPACKET2_HDRLEN         (TPACKET_ALIGN(sizeof(struct tpacket2_hdr)) + sizeof(struct sockaddr_ll))
+
+enum tpacket_versions
+{
+        TPACKET_V1,
+        TPACKET_V2,
+};
+
 /*
    Frame structure:
 
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9f2269166687..4f059775d48f 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -186,6 +186,8 @@ struct packet_sock {
         unsigned int            pg_vec_order;
         unsigned int            pg_vec_pages;
         unsigned int            pg_vec_len;
+        enum tpacket_versions   tp_version;
+        unsigned int            tp_hdrlen;
 #endif
 };
 
@@ -201,14 +203,52 @@ struct packet_skb_cb {
 
 #ifdef CONFIG_PACKET_MMAP
 
-static inline struct tpacket_hdr *packet_lookup_frame(struct packet_sock *po, unsigned int position)
+static void *packet_lookup_frame(struct packet_sock *po, unsigned int position,
+                                 int status)
 {
         unsigned int pg_vec_pos, frame_offset;
+        union {
+                struct tpacket_hdr *h1;
+                struct tpacket2_hdr *h2;
+                void *raw;
+        } h;
 
         pg_vec_pos = position / po->frames_per_block;
         frame_offset = position % po->frames_per_block;
 
-        return (struct tpacket_hdr *)(po->pg_vec[pg_vec_pos] + (frame_offset * po->frame_size));
+        h.raw = po->pg_vec[pg_vec_pos] + (frame_offset * po->frame_size);
+        switch (po->tp_version) {
+        case TPACKET_V1:
+                if (status != h.h1->tp_status ? TP_STATUS_USER :
+                                                TP_STATUS_KERNEL)
+                        return NULL;
+                break;
+        case TPACKET_V2:
+                if (status != h.h2->tp_status ? TP_STATUS_USER :
+                                                TP_STATUS_KERNEL)
+                        return NULL;
+                break;
+        }
+        return h.raw;
+}
+
+static void __packet_set_status(struct packet_sock *po, void *frame, int status)
+{
+        union {
+                struct tpacket_hdr *h1;
+                struct tpacket2_hdr *h2;
+                void *raw;
+        } h;
+
+        h.raw = frame;
+        switch (po->tp_version) {
+        case TPACKET_V1:
+                h.h1->tp_status = status;
+                break;
+        case TPACKET_V2:
+                h.h2->tp_status = status;
+                break;
+        }
 }
 #endif
 
@@ -551,14 +591,19 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
         struct sock *sk;
         struct packet_sock *po;
         struct sockaddr_ll *sll;
-        struct tpacket_hdr *h;
+        union {
+                struct tpacket_hdr *h1;
+                struct tpacket2_hdr *h2;
+                void *raw;
+        } h;
         u8 * skb_head = skb->data;
         int skb_len = skb->len;
         unsigned int snaplen, res;
         unsigned long status = TP_STATUS_LOSING|TP_STATUS_USER;
-        unsigned short macoff, netoff;
+        unsigned short macoff, netoff, hdrlen;
         struct sk_buff *copy_skb = NULL;
         struct timeval tv;
+        struct timespec ts;
 
         if (skb->pkt_type == PACKET_LOOPBACK)
                 goto drop;
@@ -590,10 +635,11 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
                 snaplen = res;
 
         if (sk->sk_type == SOCK_DGRAM) {
-                macoff = netoff = TPACKET_ALIGN(TPACKET_HDRLEN) + 16;
+                macoff = netoff = TPACKET_ALIGN(po->tp_hdrlen) + 16;
         } else {
                 unsigned maclen = skb_network_offset(skb);
-                netoff = TPACKET_ALIGN(TPACKET_HDRLEN + (maclen < 16 ? 16 : maclen));
+                netoff = TPACKET_ALIGN(po->tp_hdrlen +
+                                       (maclen < 16 ? 16 : maclen));
                 macoff = netoff - maclen;
         }
 
@@ -616,9 +662,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
         }
 
         spin_lock(&sk->sk_receive_queue.lock);
-        h = packet_lookup_frame(po, po->head);
-
-        if (h->tp_status)
+        h.raw = packet_lookup_frame(po, po->head, TP_STATUS_KERNEL);
+        if (!h.raw)
                 goto ring_is_full;
         po->head = po->head != po->frame_max ? po->head+1 : 0;
         po->stats.tp_packets++;
@@ -630,20 +675,40 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
                 status &= ~TP_STATUS_LOSING;
         spin_unlock(&sk->sk_receive_queue.lock);
 
-        skb_copy_bits(skb, 0, (u8*)h + macoff, snaplen);
+        skb_copy_bits(skb, 0, h.raw + macoff, snaplen);
 
-        h->tp_len = skb->len;
-        h->tp_snaplen = snaplen;
-        h->tp_mac = macoff;
-        h->tp_net = netoff;
-        if (skb->tstamp.tv64)
-                tv = ktime_to_timeval(skb->tstamp);
-        else
-                do_gettimeofday(&tv);
-        h->tp_sec = tv.tv_sec;
-        h->tp_usec = tv.tv_usec;
+        switch (po->tp_version) {
+        case TPACKET_V1:
+                h.h1->tp_len = skb->len;
+                h.h1->tp_snaplen = snaplen;
+                h.h1->tp_mac = macoff;
+                h.h1->tp_net = netoff;
+                if (skb->tstamp.tv64)
+                        tv = ktime_to_timeval(skb->tstamp);
+                else
+                        do_gettimeofday(&tv);
+                h.h1->tp_sec = tv.tv_sec;
+                h.h1->tp_usec = tv.tv_usec;
+                hdrlen = sizeof(*h.h1);
+                break;
+        case TPACKET_V2:
+                h.h2->tp_len = skb->len;
+                h.h2->tp_snaplen = snaplen;
+                h.h2->tp_mac = macoff;
+                h.h2->tp_net = netoff;
+                if (skb->tstamp.tv64)
+                        ts = ktime_to_timespec(skb->tstamp);
+                else
+                        getnstimeofday(&ts);
+                h.h2->tp_sec = ts.tv_sec;
+                h.h2->tp_nsec = ts.tv_nsec;
+                hdrlen = sizeof(*h.h2);
+                break;
+        default:
+                BUG();
+        }
 
-        sll = (struct sockaddr_ll*)((u8*)h + TPACKET_ALIGN(sizeof(*h)));
+        sll = h.raw + TPACKET_ALIGN(hdrlen);
         sll->sll_halen = dev_parse_header(skb, sll->sll_addr);
         sll->sll_family = AF_PACKET;
         sll->sll_hatype = dev->type;
@@ -654,14 +719,14 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
         else
                 sll->sll_ifindex = dev->ifindex;
 
-        h->tp_status = status;
+        __packet_set_status(po, h.raw, status);
         smp_mb();
 
         {
                 struct page *p_start, *p_end;
-                u8 *h_end = (u8 *)h + macoff + snaplen - 1;
+                u8 *h_end = h.raw + macoff + snaplen - 1;
 
-                p_start = virt_to_page(h);
+                p_start = virt_to_page(h.raw);
                 p_end = virt_to_page(h_end);
                 while (p_start <= p_end) {
                         flush_dcache_page(p_start);
@@ -1362,6 +1427,25 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
                 pkt_sk(sk)->copy_thresh = val;
                 return 0;
         }
+        case PACKET_VERSION:
+        {
+                int val;
+
+                if (optlen != sizeof(val))
+                        return -EINVAL;
+                if (po->pg_vec)
+                        return -EBUSY;
+                if (copy_from_user(&val, optval, sizeof(val)))
+                        return -EFAULT;
+                switch (val) {
+                case TPACKET_V1:
+                case TPACKET_V2:
+                        po->tp_version = val;
+                        return 0;
+                default:
+                        return -EINVAL;
+                }
+        }
 #endif
         case PACKET_AUXDATA:
         {
@@ -1437,6 +1521,31 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 
                 data = &val;
                 break;
+#ifdef CONFIG_PACKET_MMAP
+        case PACKET_VERSION:
+                if (len > sizeof(int))
+                        len = sizeof(int);
+                val = po->tp_version;
+                data = &val;
+                break;
+        case PACKET_HDRLEN:
+                if (len > sizeof(int))
+                        len = sizeof(int);
+                if (copy_from_user(&val, optval, len))
+                        return -EFAULT;
+                switch (val) {
+                case TPACKET_V1:
+                        val = sizeof(struct tpacket_hdr);
+                        break;
+                case TPACKET_V2:
+                        val = sizeof(struct tpacket2_hdr);
+                        break;
+                default:
+                        return -EINVAL;
+                }
+                data = &val;
+                break;
+#endif
         default:
                 return -ENOPROTOOPT;
         }
@@ -1570,11 +1679,8 @@ static unsigned int packet_poll(struct file * file, struct socket *sock,
         spin_lock_bh(&sk->sk_receive_queue.lock);
         if (po->pg_vec) {
                 unsigned last = po->head ? po->head-1 : po->frame_max;
-                struct tpacket_hdr *h;
-
-                h = packet_lookup_frame(po, last);
 
-                if (h->tp_status)
+                if (packet_lookup_frame(po, last, TP_STATUS_USER))
                         mask |= POLLIN | POLLRDNORM;
         }
         spin_unlock_bh(&sk->sk_receive_queue.lock);
@@ -1669,11 +1775,20 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
                 if (unlikely(po->pg_vec))
                         return -EBUSY;
 
+                switch (po->tp_version) {
+                case TPACKET_V1:
+                        po->tp_hdrlen = TPACKET_HDRLEN;
+                        break;
+                case TPACKET_V2:
+                        po->tp_hdrlen = TPACKET2_HDRLEN;
+                        break;
+                }
+
                 if (unlikely((int)req->tp_block_size <= 0))
                         return -EINVAL;
                 if (unlikely(req->tp_block_size & (PAGE_SIZE - 1)))
                         return -EINVAL;
-                if (unlikely(req->tp_frame_size < TPACKET_HDRLEN))
+                if (unlikely(req->tp_frame_size < po->tp_hdrlen))
                         return -EINVAL;
                 if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
                         return -EINVAL;
@@ -1692,13 +1807,11 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
                         goto out;
 
                 for (i = 0; i < req->tp_block_nr; i++) {
-                        char *ptr = pg_vec[i];
-                        struct tpacket_hdr *header;
+                        void *ptr = pg_vec[i];
                         int k;
 
                         for (k = 0; k < po->frames_per_block; k++) {
-                                header = (struct tpacket_hdr *) ptr;
-                                header->tp_status = TP_STATUS_KERNEL;
+                                __packet_set_status(po, ptr, TP_STATUS_KERNEL);
                                 ptr += req->tp_frame_size;
                         }
                 }