Add support for connected AF_INET sockets

Add support for connected AF_INET sockets

[Dan Smith]

This updated patch set includes fixes for patch 1, fixes and sanity checking
for patch 2, and the previous (unchanged) documentation patch as 3.  I've
not included the TCP time stamp patch and plan to experiment with a few
options discussed on IRC.  Whatever that is will be a separate patch anyway.

[PATCH 2/3] [RFC] Add c/r support for connected INET sockets (v3)

[Dan Smith]

This patch adds basic support for C/R of open INET sockets.  I think that
all the important bits of the TCP and ICSK socket structures is saved,
but I think there is still some additional IPv6 stuff that needs to be
handled.

With this patch applied, the following script can be used to demonstrate
the functionality:

  https://lists.linux-foundation.org/pipermail/containers/2009-October/021239.html

It shows that this enables migration of a sendmail process with open
connections from one machine to another without dropping.

We probably need comments from the netdev people about the quality of
sanity checking we do on the values in the ckpt_hdr_socket_inet
structure on restart.

Note that this still doesn't address lingering sockets yet.

Changes in v3:
 - Prevent restart from allowing a bind on a <1024 port unless the
   user is granted that capability
 - Add some sanity checking in the inet_precheck() function to make sure
   the values read from the checkpoint image are within acceptable ranges
 - Check the result of sock_restore_header_info() and fail if needed

Changes in v2:
 - Restore saddr, rcv_saddr, daddr, sport, and dport from the sockaddr
   structure instead of saving them separately
 - Fix 'sock' naming in sock_cptrst()
 - Don't take the queue lock before skb_queue_tail() since it is
   done for us
 - Allow "listen only" restore behavior if RESTART_SOCK_LISTENONLY
   flag is specified on sys_restart()
 - Pull the implementation of the list of listening sockets back into
   this patch
 - Fix dangling printk
 - Add some comments around the parent/child restore logic

Cc: netdev@vger.kernel.org
Cc: Oren Laadan <orenl@librato.com>
Cc: John Dykstra <jdykstra72@gmail.com>
Signed-off-by: Dan Smith <danms@us.ibm.com>
---
 checkpoint/sys.c                 |    4 +
 include/linux/checkpoint.h       |    5 +-
 include/linux/checkpoint_hdr.h   |   95 ++++++++++
 include/linux/checkpoint_types.h |    2 +
 net/checkpoint.c                 |   23 ++--
 net/ipv4/checkpoint.c            |  349 +++++++++++++++++++++++++++++++++++++-
 6 files changed, 463 insertions(+), 15 deletions(-)

diff --git a/checkpoint/sys.c b/checkpoint/sys.c
index 260a1ee..df00973 100644
--- a/checkpoint/sys.c
+++ b/checkpoint/sys.c
@@ -221,6 +221,8 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
 
 	kfree(ctx->pids_arr);
 
+	sock_listening_list_free(&ctx->listen_sockets);
+
 	kfree(ctx);
 }
 
@@ -249,6 +251,8 @@ static struct ckpt_ctx *ckpt_ctx_alloc(int fd, unsigned long uflags,
 	spin_lock_init(&ctx->lock);
 #endif
 
+	INIT_LIST_HEAD(&ctx->listen_sockets);
+
 	err = -EBADF;
 	ctx->file = fget(fd);
 	if (!ctx->file)
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index c2832ac..8702307 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -19,6 +19,7 @@
 #define RESTART_TASKSELF	0x1
 #define RESTART_FROZEN		0x2
 #define RESTART_GHOST		0x4
+#define RESTART_SOCK_LISTENONLY 0x8
 
 #ifdef __KERNEL__
 #ifdef CONFIG_CHECKPOINT
@@ -48,7 +49,8 @@
 #define RESTART_USER_FLAGS  \
 	(RESTART_TASKSELF | \
 	 RESTART_FROZEN | \
-	 RESTART_GHOST)
+	 RESTART_GHOST | \
+	 RESTART_SOCK_LISTENONLY)
 
 extern int walk_task_subtree(struct task_struct *task,
 			     int (*func)(struct task_struct *, void *),
@@ -102,6 +104,7 @@ extern int ckpt_sock_getnames(struct ckpt_ctx *ctx,
 			      struct sockaddr *rem, unsigned *rem_len);
 int sock_restore_header_info(struct sk_buff *skb,
 			     struct ckpt_hdr_socket_buffer *h);
+void sock_listening_list_free(struct list_head *head);
 
 /* ckpt kflags */
 #define ckpt_set_ctx_kflag(__ctx, __kflag)  \
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 3e6cab1..e0f6d25 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -20,6 +20,7 @@
 #include <linux/socket.h>
 #include <linux/un.h>
 #include <linux/in.h>
+#include <linux/in6.h>
 #else
 #include <sys/socket.h>
 #include <sys/un.h>
@@ -569,6 +570,100 @@ struct ckpt_hdr_socket_unix {
 
 struct ckpt_hdr_socket_inet {
 	struct ckpt_hdr h;
+	__u32 daddr;
+	__u32 rcv_saddr;
+	__u32 saddr;
+	__u16 dport;
+	__u16 num;
+	__u16 sport;
+	__s16 uc_ttl;
+	__u16 cmsg_flags;
+
+	struct {
+		__u64 timeout;
+		__u32 ato;
+		__u32 lrcvtime;
+		__u16 last_seg_size;
+		__u16 rcv_mss;
+		__u8 pending;
+		__u8 quick;
+		__u8 pingpong;
+		__u8 blocked;
+	} icsk_ack __attribute__ ((aligned(8)));
+
+	/* FIXME: Skipped opt, tos, multicast, cork settings */
+
+	struct {
+		__u32 rcv_nxt;
+		__u32 copied_seq;
+		__u32 rcv_wup;
+		__u32 snd_nxt;
+		__u32 snd_una;
+		__u32 snd_sml;
+		__u32 rcv_tstamp;
+		__u32 lsndtime;
+
+		__u32 snd_wl1;
+		__u32 snd_wnd;
+		__u32 max_window;
+		__u32 mss_cache;
+		__u32 window_clamp;
+		__u32 rcv_ssthresh;
+		__u32 frto_highmark;
+
+		__u32 srtt;
+		__u32 mdev;
+		__u32 mdev_max;
+		__u32 rttvar;
+		__u32 rtt_seq;
+
+		__u32 packets_out;
+		__u32 retrans_out;
+
+		__u32 snd_up;
+		__u32 rcv_wnd;
+		__u32 write_seq;
+		__u32 pushed_seq;
+		__u32 lost_out;
+		__u32 sacked_out;
+		__u32 fackets_out;
+		__u32 tso_deferred;
+		__u32 bytes_acked;
+
+		__s32 lost_cnt_hint;
+		__u32 retransmit_high;
+
+		__u32 lost_retrans_low;
+
+		__u32 prior_ssthresh;
+		__u32 high_seq;
+
+		__u32 retrans_stamp;
+		__u32 undo_marker;
+		__s32 undo_retrans;
+		__u32 total_retrans;
+
+		__u32 urg_seq;
+		__u32 keepalive_time;
+		__u32 keepalive_intvl;
+
+		__u16 urg_data;
+		__u16 advmss;
+		__u8 frto_counter;
+		__u8 nonagle;
+
+		__u8 ecn_flags;
+		__u8 reordering;
+
+		__u8 keepalive_probes;
+	} tcp __attribute__ ((aligned(8)));
+
+	struct {
+		struct in6_addr saddr;
+		struct in6_addr rcv_saddr;
+		struct in6_addr daddr;
+	} inet6 __attribute__ ((aligned(8)));
+
 	__u32 laddr_len;
 	__u32 raddr_len;
 	struct sockaddr_in laddr;
diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
index fa57cdc..91c141b 100644
--- a/include/linux/checkpoint_types.h
+++ b/include/linux/checkpoint_types.h
@@ -65,6 +65,8 @@ struct ckpt_ctx {
 	struct list_head pgarr_list;	/* page array to dump VMA contents */
 	struct list_head pgarr_pool;	/* pool of empty page arrays chain */
 
+	struct list_head listen_sockets;/* listening parent sockets */
+
 	/* [multi-process checkpoint] */
 	struct task_struct **tasks_arr; /* array of all tasks [checkpoint] */
 	int nr_tasks;                   /* size of tasks array */
diff --git a/net/checkpoint.c b/net/checkpoint.c
index 50baea9..98ba083 100644
--- a/net/checkpoint.c
+++ b/net/checkpoint.c
@@ -134,6 +134,7 @@ int sock_restore_header_info(struct sk_buff *skb,
 
 static int __sock_write_buffers(struct ckpt_ctx *ctx,
 				struct sk_buff_head *queue,
+				uint16_t family,
 				int dst_objref)
 {
 	struct sk_buff *skb;
@@ -142,11 +143,7 @@ static int __sock_write_buffers(struct ckpt_ctx *ctx,
 		struct ckpt_hdr_socket_buffer *h;
 		int ret = 0;
 
-		/* FIXME: This could be a false positive for non-unix
-		 *        buffers, so add a type check here in the
-		 *        future
-		 */
-		if (UNIXCB(skb).fp) {
+		if ((family == AF_UNIX) && UNIXCB(skb).fp) {
 			ckpt_write_err(ctx, "TE", "af_unix: pass fd", -EBUSY);
 			return -EBUSY;
 		}
@@ -186,6 +183,7 @@ static int __sock_write_buffers(struct ckpt_ctx *ctx,
 
 static int sock_write_buffers(struct ckpt_ctx *ctx,
 			      struct sk_buff_head *queue,
+			      uint16_t family,
 			      int dst_objref)
 {
 	struct ckpt_hdr_socket_queue *h;
@@ -205,7 +203,7 @@ static int sock_write_buffers(struct ckpt_ctx *ctx,
 	h->skb_count = ret;
 	ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) h);
 	if (!ret)
-		ret = __sock_write_buffers(ctx, &tmpq, dst_objref);
+		ret = __sock_write_buffers(ctx, &tmpq, family, dst_objref);
 
  out:
 	ckpt_hdr_put(ctx, h);
@@ -227,12 +225,14 @@ int sock_deferred_write_buffers(void *data)
 		return dst_objref;
 	}
 
-	ret = sock_write_buffers(ctx, &dq->sk->sk_receive_queue, dst_objref);
+	ret = sock_write_buffers(ctx, &dq->sk->sk_receive_queue,
+				 dq->sk->sk_family, dst_objref);
 	ckpt_debug("write recv buffers: %i\n", ret);
 	if (ret < 0)
 		return ret;
 
-	ret = sock_write_buffers(ctx, &dq->sk->sk_write_queue, dst_objref);
+	ret = sock_write_buffers(ctx, &dq->sk->sk_write_queue,
+				 dq->sk->sk_family, dst_objref);
 	ckpt_debug("write send buffers: %i\n", ret);
 
 	return ret;
@@ -757,10 +757,9 @@ struct sock *do_sock_restore(struct ckpt_ctx *ctx)
 		goto err;
 
 	if ((h->sock_common.family == AF_INET) &&
-	    (h->sock.state != TCP_LISTEN)) {
-		/* Temporary hack to enable restore of TCP_LISTEN sockets
-		 * while forcing anything else to a closed state
-		 */
+	    (h->sock.state != TCP_LISTEN) &&
+	    (ctx->uflags & RESTART_SOCK_LISTENONLY)) {
+		ckpt_debug("Forcing open socket closed\n");
 		sock->sk->sk_state = TCP_CLOSE;
 		sock->state = SS_UNCONNECTED;
 	}
diff --git a/net/ipv4/checkpoint.c b/net/ipv4/checkpoint.c
index 9cbbf5e..671014b 100644
--- a/net/ipv4/checkpoint.c
+++ b/net/ipv4/checkpoint.c
@@ -17,6 +17,7 @@
 #include <linux/deferqueue.h>
 #include <net/tcp_states.h>
 #include <net/tcp.h>
+#include <net/ipv6.h>
 
 struct dq_sock {
 	struct ckpt_ctx *ctx;
@@ -28,6 +29,233 @@ struct dq_buffers {
 	struct sock *sk;
 };
 
+struct listen_item {
+	struct sock *sk;
+	struct list_head list;
+};
+
+void sock_listening_list_free(struct list_head *head)
+{
+	struct listen_item *item, *tmp;
+
+	list_for_each_entry_safe(item, tmp, head, list) {
+		list_del(&item->list);
+		kfree(item);
+	}
+}
+
+static int sock_listening_list_add(struct ckpt_ctx *ctx, struct sock *sk)
+{
+	struct listen_item *item;
+
+	item = kmalloc(sizeof(*item), GFP_KERNEL);
+	if (!item)
+		return -ENOMEM;
+
+	item->sk = sk;
+	list_add(&item->list, &ctx->listen_sockets);
+
+	return 0;
+}
+
+static struct sock *sock_get_parent(struct ckpt_ctx *ctx, struct sock *sk)
+{
+	struct listen_item *item;
+
+	list_for_each_entry(item, &ctx->listen_sockets, list) {
+		if (inet_sk(sk)->sport == inet_sk(item->sk)->sport)
+			return item->sk;
+	}
+
+	return NULL;
+}
+
+static int sock_hash_parent(void *data)
+{
+	struct dq_sock *dq = (struct dq_sock *)data;
+	struct sock *parent;
+
+	ckpt_debug("INET post-restart hash\n");
+
+	dq->sk->sk_prot->hash(dq->sk);
+
+	/* If there is a listening socket with the same source port,
+	 * then become a child of that socket [we are the result of an
+	 * accept()].  Otherwise hash ourselves directly in [we are
+	 * the result of a connect()]
+	 */
+
+	parent = sock_get_parent(dq->ctx, dq->sk);
+	if (parent) {
+		inet_sk(dq->sk)->num = ntohs(inet_sk(dq->sk)->sport);
+		local_bh_disable();
+		__inet_inherit_port(parent, dq->sk);
+		local_bh_enable();
+	} else {
+		inet_sk(dq->sk)->num = 0;
+		inet_hash_connect(&tcp_death_row, dq->sk);
+		inet_sk(dq->sk)->num = ntohs(inet_sk(dq->sk)->sport);
+	}
+
+	return 0;
+}
+
+static int sock_defer_hash(struct ckpt_ctx *ctx, struct sock *sock)
+{
+	struct dq_sock dq;
+
+	dq.sk = sock;
+	dq.ctx = ctx;
+
+	return deferqueue_add(ctx->deferqueue, &dq, sizeof(dq),
+			      sock_hash_parent, NULL);
+}
+
+static int sock_inet_tcp_cptrst(struct ckpt_ctx *ctx,
+				struct tcp_sock *sk,
+				struct ckpt_hdr_socket_inet *hh,
+				int op)
+{
+	CKPT_COPY(op, hh->tcp.rcv_nxt, sk->rcv_nxt);
+	CKPT_COPY(op, hh->tcp.copied_seq, sk->copied_seq);
+	CKPT_COPY(op, hh->tcp.rcv_wup, sk->rcv_wup);
+	CKPT_COPY(op, hh->tcp.snd_nxt, sk->snd_nxt);
+	CKPT_COPY(op, hh->tcp.snd_una, sk->snd_una);
+	CKPT_COPY(op, hh->tcp.snd_sml, sk->snd_sml);
+	CKPT_COPY(op, hh->tcp.rcv_tstamp, sk->rcv_tstamp);
+	CKPT_COPY(op, hh->tcp.lsndtime, sk->lsndtime);
+
+	CKPT_COPY(op, hh->tcp.snd_wl1, sk->snd_wl1);
+	CKPT_COPY(op, hh->tcp.snd_wnd, sk->snd_wnd);
+	CKPT_COPY(op, hh->tcp.max_window, sk->max_window);
+	CKPT_COPY(op, hh->tcp.mss_cache, sk->mss_cache);
+	CKPT_COPY(op, hh->tcp.window_clamp, sk->window_clamp);
+	CKPT_COPY(op, hh->tcp.rcv_ssthresh, sk->rcv_ssthresh);
+	CKPT_COPY(op, hh->tcp.frto_highmark, sk->frto_highmark);
+	CKPT_COPY(op, hh->tcp.advmss, sk->advmss);
+	CKPT_COPY(op, hh->tcp.frto_counter, sk->frto_counter);
+	CKPT_COPY(op, hh->tcp.nonagle, sk->nonagle);
+
+	CKPT_COPY(op, hh->tcp.srtt, sk->srtt);
+	CKPT_COPY(op, hh->tcp.mdev, sk->mdev);
+	CKPT_COPY(op, hh->tcp.mdev_max, sk->mdev_max);
+	CKPT_COPY(op, hh->tcp.rttvar, sk->rttvar);
+	CKPT_COPY(op, hh->tcp.rtt_seq, sk->rtt_seq);
+
+	CKPT_COPY(op, hh->tcp.packets_out, sk->packets_out);
+	CKPT_COPY(op, hh->tcp.retrans_out, sk->retrans_out);
+
+	CKPT_COPY(op, hh->tcp.urg_data, sk->urg_data);
+	CKPT_COPY(op, hh->tcp.ecn_flags, sk->ecn_flags);
+	CKPT_COPY(op, hh->tcp.reordering, sk->reordering);
+	CKPT_COPY(op, hh->tcp.snd_up, sk->snd_up);
+
+	CKPT_COPY(op, hh->tcp.keepalive_probes, sk->keepalive_probes);
+
+	CKPT_COPY(op, hh->tcp.rcv_wnd, sk->rcv_wnd);
+	CKPT_COPY(op, hh->tcp.write_seq, sk->write_seq);
+	CKPT_COPY(op, hh->tcp.pushed_seq, sk->pushed_seq);
+	CKPT_COPY(op, hh->tcp.lost_out, sk->lost_out);
+	CKPT_COPY(op, hh->tcp.sacked_out, sk->sacked_out);
+	CKPT_COPY(op, hh->tcp.fackets_out, sk->fackets_out);
+	CKPT_COPY(op, hh->tcp.tso_deferred, sk->tso_deferred);
+	CKPT_COPY(op, hh->tcp.bytes_acked, sk->bytes_acked);
+
+	CKPT_COPY(op, hh->tcp.lost_cnt_hint, sk->lost_cnt_hint);
+	CKPT_COPY(op, hh->tcp.retransmit_high, sk->retransmit_high);
+
+	CKPT_COPY(op, hh->tcp.lost_retrans_low, sk->lost_retrans_low);
+
+	CKPT_COPY(op, hh->tcp.prior_ssthresh, sk->prior_ssthresh);
+	CKPT_COPY(op, hh->tcp.high_seq, sk->high_seq);
+
+	CKPT_COPY(op, hh->tcp.retrans_stamp, sk->retrans_stamp);
+	CKPT_COPY(op, hh->tcp.undo_marker, sk->undo_marker);
+	CKPT_COPY(op, hh->tcp.undo_retrans, sk->undo_retrans);
+	CKPT_COPY(op, hh->tcp.total_retrans, sk->total_retrans);
+
+	CKPT_COPY(op, hh->tcp.urg_seq, sk->urg_seq);
+	CKPT_COPY(op, hh->tcp.keepalive_time, sk->keepalive_time);
+	CKPT_COPY(op, hh->tcp.keepalive_intvl, sk->keepalive_intvl);
+
+	return 0;
+}
+
+static int sock_inet_restore_addrs(struct inet_sock *inet,
+				   struct ckpt_hdr_socket_inet *hh)
+{
+	inet->daddr = hh->raddr.sin_addr.s_addr;
+	inet->saddr = hh->laddr.sin_addr.s_addr;
+	inet->rcv_saddr = inet->saddr;
+
+	inet->dport = hh->raddr.sin_port;
+	inet->sport = hh->laddr.sin_port;
+
+	return 0;
+}
+
+static int sock_inet_cptrst(struct ckpt_ctx *ctx,
+			    struct sock *sk,
+			    struct ckpt_hdr_socket_inet *hh,
+			    int op)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	int ret;
+
+	if (op == CKPT_CPT) {
+		CKPT_COPY(op, hh->daddr, inet->daddr);
+		CKPT_COPY(op, hh->rcv_saddr, inet->rcv_saddr);
+		CKPT_COPY(op, hh->dport, inet->dport);
+		CKPT_COPY(op, hh->saddr, inet->saddr);
+		CKPT_COPY(op, hh->sport, inet->sport);
+	} else {
+		ret = sock_inet_restore_addrs(inet, hh);
+		if (ret)
+			return ret;
+	}
+
+	CKPT_COPY(op, hh->num, inet->num);
+	CKPT_COPY(op, hh->uc_ttl, inet->uc_ttl);
+	CKPT_COPY(op, hh->cmsg_flags, inet->cmsg_flags);
+
+	CKPT_COPY(op, hh->icsk_ack.pending, icsk->icsk_ack.pending);
+	CKPT_COPY(op, hh->icsk_ack.quick, icsk->icsk_ack.quick);
+	CKPT_COPY(op, hh->icsk_ack.pingpong, icsk->icsk_ack.pingpong);
+	CKPT_COPY(op, hh->icsk_ack.blocked, icsk->icsk_ack.blocked);
+	CKPT_COPY(op, hh->icsk_ack.ato, icsk->icsk_ack.ato);
+	CKPT_COPY(op, hh->icsk_ack.timeout, icsk->icsk_ack.timeout);
+	CKPT_COPY(op, hh->icsk_ack.lrcvtime, icsk->icsk_ack.lrcvtime);
+	CKPT_COPY(op,
+		  hh->icsk_ack.last_seg_size, icsk->icsk_ack.last_seg_size);
+	CKPT_COPY(op, hh->icsk_ack.rcv_mss, icsk->icsk_ack.rcv_mss);
+
+	if (sk->sk_protocol == IPPROTO_TCP)
+		ret = sock_inet_tcp_cptrst(ctx, tcp_sk(sk), hh, op);
+	else if (sk->sk_protocol == IPPROTO_UDP)
+		ret = 0;
+	else {
+		ckpt_write_err(ctx, "T", "unknown socket protocol %d",
+			       sk->sk_protocol);
+		ret = -EINVAL;
+	}
+
+	if (sk->sk_family == AF_INET6) {
+		struct ipv6_pinfo *inet6 = inet6_sk(sk);
+		if (op == CKPT_CPT) {
+			ipv6_addr_copy(&hh->inet6.saddr, &inet6->saddr);
+			ipv6_addr_copy(&hh->inet6.rcv_saddr, &inet6->rcv_saddr);
+			ipv6_addr_copy(&hh->inet6.daddr, &inet6->daddr);
+		} else {
+			ipv6_addr_copy(&inet6->saddr, &hh->inet6.saddr);
+			ipv6_addr_copy(&inet6->rcv_saddr, &hh->inet6.rcv_saddr);
+			ipv6_addr_copy(&inet6->daddr, &hh->inet6.daddr);
+		}
+	}
+
+	return ret;
+}
+
 int inet_checkpoint(struct ckpt_ctx *ctx, struct socket *sock)
 {
 	struct ckpt_hdr_socket_inet *in;
@@ -43,6 +271,10 @@ int inet_checkpoint(struct ckpt_ctx *ctx, struct socket *sock)
 	if (ret)
 		goto out;
 
+	ret = sock_inet_cptrst(ctx, sock->sk, in, CKPT_CPT);
+	if (ret < 0)
+		goto out;
+
 	ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) in);
  out:
 	ckpt_hdr_put(ctx, in);
@@ -87,9 +319,11 @@ static int inet_read_buffer(struct ckpt_ctx *ctx, struct sk_buff_head *queue)
 	if (ret < 0)
 		goto out;
 
-	spin_lock(&queue->lock);
+	ret = sock_restore_header_info(skb, h);
+	if (!ret)
+		goto out;
+
 	skb_queue_tail(queue, skb);
-	spin_unlock(&queue->lock);
  out:
 	ckpt_hdr_put(ctx, h);
 
@@ -162,6 +396,19 @@ static int inet_defer_restore_buffers(struct ckpt_ctx *ctx, struct sock *sk)
 
 static int inet_precheck(struct socket *sock, struct ckpt_hdr_socket_inet *in)
 {
+	__u8 icsk_ack_mask = ICSK_ACK_SCHED | ICSK_ACK_TIMER |
+		ICSK_ACK_PUSHED | ICSK_ACK_PUSHED2;
+	__u16 urg_mask = TCP_URG_VALID | TCP_URG_NOTYET | TCP_URG_READ;
+	__u8 nonagle_mask = TCP_NAGLE_OFF | TCP_NAGLE_CORK | TCP_NAGLE_PUSH;
+	__u8 ecn_mask = TCP_ECN_OK | TCP_ECN_QUEUE_CWR | TCP_ECN_DEMAND_CWR;
+
+	if ((htons(in->laddr.sin_port) < PROT_SOCK) &&
+	    !capable(CAP_NET_BIND_SERVICE)) {
+		ckpt_debug("unable to bind to port %hu\n",
+			   htons(in->laddr.sin_port));
+		return -EINVAL;
+	}
+
 	if (in->laddr_len > sizeof(struct sockaddr_in)) {
 		ckpt_debug("laddr_len is too big\n");
 		return -EINVAL;
@@ -172,6 +419,77 @@ static int inet_precheck(struct socket *sock, struct ckpt_hdr_socket_inet *in)
 		return -EINVAL;
 	}
 
+	/* Set ato to the default */
+	in->icsk_ack.ato = TCP_ATO_MIN;
+
+	/* No quick acks are scheduled after a restart */
+	in->icsk_ack.quick = 0;
+
+	if (in->icsk_ack.pending & ~icsk_ack_mask) {
+		ckpt_debug("invalid pending flags 0x%x\n",
+			   in->icsk_ack.pending & ~icsk_ack_mask);
+		return -EINVAL;
+	}
+
+	if (in->icsk_ack.pingpong > 1) {
+		ckpt_debug("invalid icsk_ack.pingpong value\n");
+		return -EINVAL;
+	}
+
+	if (in->icsk_ack.blocked > 1) {
+		ckpt_debug("invalid icsk_ack.blocked value\n");
+		return -EINVAL;
+	}
+
+	/* do_tcp_setsockopt() quietly makes this coercion */
+	if (in->tcp.window_clamp < (SOCK_MIN_RCVBUF / 2))
+		in->tcp.window_clamp = SOCK_MIN_RCVBUF / 2;
+	else if (in->tcp.window_clamp > 65535U) {
+		ckpt_debug("invalid window_clamp value\n");
+		return -EINVAL;
+	}
+
+	if (in->tcp.rcv_ssthresh > (4U * in->tcp.advmss))
+		in->tcp.rcv_ssthresh = 4U * in->tcp.advmss;
+
+	/* These will all be recalculated on the next call to
+	 * tcp_rtt_estimator()
+	 */
+	in->tcp.srtt = in->tcp.mdev = in->tcp.mdev_max = 0;
+	in->tcp.rttvar = in->tcp.rtt_seq = 0;
+
+	/* Might want to set packets_out to zero ? */
+
+	if (in->tcp.rcv_wnd > MAX_TCP_WINDOW)
+		in->tcp.rcv_wnd = MAX_TCP_WINDOW;
+
+	if (in->tcp.keepalive_intvl > MAX_TCP_KEEPINTVL) {
+		ckpt_debug("keepalive_intvl %i out of range\n",
+			   in->tcp.keepalive_intvl);
+		return -EINVAL;
+	}
+
+	if (in->tcp.keepalive_probes > MAX_TCP_KEEPCNT) {
+		ckpt_debug("Invalid keepalive_probes value %i\n",
+			   in->tcp.keepalive_probes);
+		return -EINVAL;
+	}
+
+	if (in->tcp.urg_data & ~urg_mask) {
+		ckpt_debug("Invalid urg_data value\n");
+		return -EINVAL;
+	}
+
+	if (in->tcp.nonagle & ~nonagle_mask) {
+		ckpt_debug("Invalid nonagle value\n");
+		return -EINVAL;
+	}
+
+	if (in->tcp.ecn_flags & ~ecn_mask) {
+		ckpt_debug("Invalid ecn_flags value\n");
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
@@ -209,8 +527,35 @@ int inet_restore(struct ckpt_ctx *ctx,
 			ckpt_debug("inet listen: %i\n", ret);
 			if (ret < 0)
 				goto out;
+
+			/* We are a listening socket, so add ourselves
+			 * to the list of parent sockets.  This will
+			 * allow our children to find us later and
+			 * link up
+			 */
+
+			ret = sock_listening_list_add(ctx, sock->sk);
+			if (ret < 0)
+				goto out;
 		}
 	} else {
+		ret = sock_inet_cptrst(ctx, sock->sk, in, CKPT_RST);
+		if (ret)
+			goto out;
+
+		if ((h->sock.state == TCP_ESTABLISHED) &&
+		    (h->sock.protocol == IPPROTO_TCP)) {
+			/* A connected socket that was spawned from an
+			 * accept() needs to be hashed with its parent
+			 * listening socket in order to receive
+			 * traffic on the original port.  Since we may
+			 * not have restarted the parent yet, we defer
+			 * this until later when we know we have all
+			 * the listening sockets accounted for.
+			 */
+			ret = sock_defer_hash(ctx, sock->sk);
+		}
+
 		if (!sock_flag(sock->sk, SOCK_DEAD))
 			ret = inet_defer_restore_buffers(ctx, sock->sk);
 	}
-- 
1.6.2.5

Re: [PATCH 2/3] [RFC] Add c/r support for connected INET sockets (v3)

[Oren Laadan]

Dan Smith wrote:
> This patch adds basic support for C/R of open INET sockets.  I think that
> all the important bits of the TCP and ICSK socket structures is saved,
> but I think there is still some additional IPv6 stuff that needs to be
> handled.
> 
> With this patch applied, the following script can be used to demonstrate
> the functionality:
> 
>   https://lists.linux-foundation.org/pipermail/containers/2009-October/021239.html
> 
> It shows that this enables migration of a sendmail process with open
> connections from one machine to another without dropping.
> 
> We probably need comments from the netdev people about the quality of
> sanity checking we do on the values in the ckpt_hdr_socket_inet
> structure on restart.
> 
> Note that this still doesn't address lingering sockets yet.
> 
> Changes in v3:
>  - Prevent restart from allowing a bind on a <1024 port unless the
>    user is granted that capability
>  - Add some sanity checking in the inet_precheck() function to make sure
>    the values read from the checkpoint image are within acceptable ranges
>  - Check the result of sock_restore_header_info() and fail if needed
> 
> Changes in v2:
>  - Restore saddr, rcv_saddr, daddr, sport, and dport from the sockaddr
>    structure instead of saving them separately
>  - Fix 'sock' naming in sock_cptrst()
>  - Don't take the queue lock before skb_queue_tail() since it is
>    done for us
>  - Allow "listen only" restore behavior if RESTART_SOCK_LISTENONLY
>    flag is specified on sys_restart()
>  - Pull the implementation of the list of listening sockets back into
>    this patch
>  - Fix dangling printk
>  - Add some comments around the parent/child restore logic
> 
> Cc: netdev@vger.kernel.org
> Cc: Oren Laadan <orenl@librato.com>
> Cc: John Dykstra <jdykstra72@gmail.com>
> Signed-off-by: Dan Smith <danms@us.ibm.com>
> ---

This looks good:
Acked-by: Oren Laadan <orenl@cs.columbia.edu>

I still want to move this to right under the restart-specific fields:
	struct list_head listen_sockets;/* listening parent sockets */

Also, I'm looking for a better name for RESTART_SOCK_LISTENONLY
(it isn't listen only, udp sockets are preserved...), something
that will convey the idea that we drop old connections,
perhaps:
	RESTART_NET_RESET
	RESTART_CONN_RESET
	RESTART_DROPCONN
?

Oren.

[PATCH 1/3] Record and restore skb header marks (v2)

[Dan Smith]

Save this information when we checkpoint an skb and provide a mechanism
to restore that information on restart.  This will be used in the
subsequent INET patch.

Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

Changes in v2:
 - Add range checks to ensure that the header marks we restore
   are within the data length of the skb
---
 include/linux/checkpoint.h     |    2 +
 include/linux/checkpoint_hdr.h |    7 ++++++
 net/checkpoint.c               |   45 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 0 deletions(-)

diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 4b61378..c2832ac 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -100,6 +100,8 @@ extern int ckpt_sock_getnames(struct ckpt_ctx *ctx,
 			      struct socket *socket,
 			      struct sockaddr *loc, unsigned *loc_len,
 			      struct sockaddr *rem, unsigned *rem_len);
+int sock_restore_header_info(struct sk_buff *skb,
+			     struct ckpt_hdr_socket_buffer *h);
 
 /* ckpt kflags */
 #define ckpt_set_ctx_kflag(__ctx, __kflag)  \
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index ca2500d..3e6cab1 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -542,8 +542,15 @@ struct ckpt_hdr_socket_queue {
 
 struct ckpt_hdr_socket_buffer {
 	struct ckpt_hdr h;
+	__u64 mac_len;
+	__u64 hdr_len;
+	__u64 transport_header;
+	__u64 network_header;
+	__u64 mac_header;
 	__s32 sk_objref;
 	__s32 pr_objref;
+	__u16 protocol;
+	__u8 cb[48];
 };
 
 #define CKPT_UNIX_LINKED 1
diff --git a/net/checkpoint.c b/net/checkpoint.c
index dd23efd..50baea9 100644
--- a/net/checkpoint.c
+++ b/net/checkpoint.c
@@ -88,6 +88,50 @@ static int sock_copy_buffers(struct sk_buff_head *from,
 	return -EAGAIN;
 }
 
+static void sock_record_header_info(struct sk_buff *skb,
+				    struct ckpt_hdr_socket_buffer *h)
+{
+
+	h->mac_len = skb->mac_len;
+	h->hdr_len = skb->hdr_len;
+
+#ifdef NET_SKBUFF_DATA_USES_OFFSET
+	h->transport_header = skb->transport_hdr;
+	h->network_header = skb->network_header;
+	h->mac_header = skb->mac_header;
+#else
+	h->transport_header = skb->transport_header - skb->head;
+	h->network_header = skb->network_header - skb->head;
+	h->mac_header = skb->mac_header - skb->head;
+#endif
+
+	memcpy(h->cb, skb->cb, sizeof(skb->cb));
+}
+
+int sock_restore_header_info(struct sk_buff *skb,
+			     struct ckpt_hdr_socket_buffer *h)
+{
+	if ((h->transport_header >= skb->len) ||
+	    (h->network_header >= skb->len) ||
+	    (h->mac_header >= skb->len) ||
+	    (h->mac_len >= skb->len) ||
+	    (h->hdr_len >= skb->len)) {
+		ckpt_debug("skb header positions not within data length\n");
+		return -EINVAL;
+	}
+
+	skb->mac_len = h->mac_len;
+	skb->hdr_len = h->hdr_len;
+
+	skb_set_transport_header(skb, h->transport_header);
+	skb_set_network_header(skb, h->network_header);
+	skb_set_mac_header(skb, h->mac_header);
+
+	memcpy(skb->cb, h->cb, sizeof(skb->cb));
+
+	return 0;
+}
+
 static int __sock_write_buffers(struct ckpt_ctx *ctx,
 				struct sk_buff_head *queue,
 				int dst_objref)
@@ -123,6 +167,7 @@ static int __sock_write_buffers(struct ckpt_ctx *ctx,
 			goto end;
 		h->sk_objref = ret;
 		h->pr_objref = dst_objref;
+		sock_record_header_info(skb, h);
 
 		ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) h);
 		if (ret < 0)
-- 
1.6.2.5

Re: [PATCH 1/3] Record and restore skb header marks (v2)

[Oren Laadan]

Dan Smith wrote:
> Save this information when we checkpoint an skb and provide a mechanism
> to restore that information on restart.  This will be used in the
> subsequent INET patch.
> 
> Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> 
> Changes in v2:
>  - Add range checks to ensure that the header marks we restore
>    are within the data length of the skb

[...]

> +int sock_restore_header_info(struct sk_buff *skb,
> +			     struct ckpt_hdr_socket_buffer *h)
> +{
> +	if ((h->transport_header >= skb->len) ||
> +	    (h->network_header >= skb->len) ||
> +	    (h->mac_header >= skb->len) ||
> +	    (h->mac_len >= skb->len) ||
> +	    (h->hdr_len >= skb->len)) {

I wonder if the sanity test for mac_len and hdr_len are sufficient,
or whether a more constrained test is required.

For example, a quick grep shows that there are several places where:
	skb->mac_len = skb->network_header - skb->mac_header;

I think there is some code that relies on it without validating
that the value makes sense.

> +		ckpt_debug("skb header positions not within data length\n");
> +		return -EINVAL;
> +	}
> +
> +	skb->mac_len = h->mac_len;
> +	skb->hdr_len = h->hdr_len;
> +
> +	skb_set_transport_header(skb, h->transport_header);
> +	skb_set_network_header(skb, h->network_header);
> +	skb_set_mac_header(skb, h->mac_header);
> +
> +	memcpy(skb->cb, h->cb, sizeof(skb->cb));

The skb->cb holds can be used by any layer to put private variables.

Can the user mangle the data in there to create a disaster of some
sort ?

If the answer is "it's possible", and because this is per protocol
data, I suggest to add a per-protocol callback to sanitize the data
in this control buffer.

To not block this patchset infinitely, I guess you can put the
details of the sanity check in a separate patch(set). But I prefer
that the current set will at least mention and provision for such
a mechanism.

> +
> +	return 0;
> +}
> +
>  static int __sock_write_buffers(struct ckpt_ctx *ctx,
>  				struct sk_buff_head *queue,
>  				int dst_objref)
> @@ -123,6 +167,7 @@ static int __sock_write_buffers(struct ckpt_ctx *ctx,
>  			goto end;
>  		h->sk_objref = ret;
>  		h->pr_objref = dst_objref;
> +		sock_record_header_info(skb, h);
>  
>  		ret = ckpt_write_obj(ctx, (struct ckpt_hdr *) h);
>  		if (ret < 0)

Oren.

Re: [PATCH 1/3] Record and restore skb header marks (v2)

[Dan Smith]

Eesh, I just realized I never replied to this mail.  Sorry about
that.

OL> I wonder if the sanity test for mac_len and hdr_len are
OL> sufficient, or whether a more constrained test is required.

Yep, I have it changed now, along with some of the other checks.

OL> The skb->cb holds can be used by any layer to put private
OL> variables.

OL> Can the user mangle the data in there to create a disaster of some
OL> sort ?

OL> If the answer is "it's possible", and because this is per protocol
OL> data, I suggest to add a per-protocol callback to sanitize the
OL> data in this control buffer.

Okay, then my answer is "it could be possible later".  Right now, I
don't think there's anything in there that could be used to do more
harm than any of the other things we restore for TCP.  We don't
restore it for UNIX sockets.

OL> To not block this patchset infinitely, I guess you can put the
OL> details of the sanity check in a separate patch(set). But I prefer
OL> that the current set will at least mention and provision for such
OL> a mechanism.

Indeed.  I've added a lengthy comment to be included in the next
posting to cover it for now.

-- 
Dan Smith
IBM Linux Technology Center
email: danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org

[PATCH 3/3] Add some content to the readme.txt for socket c/r

[Dan Smith]

Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 Documentation/checkpoint/readme.txt |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/Documentation/checkpoint/readme.txt b/Documentation/checkpoint/readme.txt
index 571c469..e6c173d 100644
--- a/Documentation/checkpoint/readme.txt
+++ b/Documentation/checkpoint/readme.txt
@@ -334,6 +334,27 @@ we will be forced to more carefully review each of those features.
 However, this can be controlled with a sysctl-variable.
 
 
+Sockets
+=======
+
+For AF_UNIX sockets, both endpoints must be within the checkpointed
+task set to maintain a connected state after restart.  UNIX sockets
+that are in the process of passing a descriptor will cause the
+checkpoint to fail with -EBUSY indicating a transient state that
+cannot be checkpointed.  Listening sockets with an unaccepted peer
+will also cause an -EBUSY result.
+
+AF_INET sockets with endpoints outside the checkpointed task set may
+remain open if care is taken to avoid TCP timeouts and resets.
+Careful use of a virtual IP address can help avoid emission of an RST
+to the non-checkpointed endpoint.  If desired, the
+RESTART_SOCK_LISTENONLY flag may be passed to the restart syscall
+which will cause all connected AF_INET sockets to be closed during the
+restore process.  Listening sockets will still be restored to their
+original state, which makes this mode a candidate for something like
+an HTTP server.
+
+
 Kernel interfaces
 =================
 
-- 
1.6.2.5