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Date: Fri, 7 Jun 2024 01:40:37 -0400
From: Christian Hopps <chopps@...pps.org>
To: devel@...ux-ipsec.org
Cc: Steffen Klassert <steffen.klassert@...unet.com>,
netdev@...r.kernel.org,
Christian Hopps <chopps@...pps.org>,
Christian Hopps <chopps@...n.net>
Subject: [PATCH ipsec-next v3 13/17] xfrm: iptfs: handle received fragmented inner packets
From: Christian Hopps <chopps@...n.net>
Add support for handling receipt of partial inner packets that have
been fragmented across multiple outer IP-TFS tunnel packets.
Signed-off-by: Christian Hopps <chopps@...n.net>
---
net/xfrm/xfrm_iptfs.c | 438 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 425 insertions(+), 13 deletions(-)
diff --git a/net/xfrm/xfrm_iptfs.c b/net/xfrm/xfrm_iptfs.c
index ad7aa4f16e8e..a8d6ce2882b3 100644
--- a/net/xfrm/xfrm_iptfs.c
+++ b/net/xfrm/xfrm_iptfs.c
@@ -55,10 +55,22 @@ struct xfrm_iptfs_data {
struct hrtimer iptfs_timer; /* output timer */
time64_t iptfs_settime; /* time timer was set */
u32 payload_mtu; /* max payload size */
+
+ /* Tunnel egress */
+ spinlock_t drop_lock;
+ struct hrtimer drop_timer;
+ u64 drop_time_ns;
+
+ /* Tunnel egress reassembly */
+ struct sk_buff *ra_newskb; /* new pkt being reassembled */
+ u64 ra_wantseq; /* expected next sequence */
+ u8 ra_runt[6]; /* last pkt bytes from last skb */
+ u8 ra_runtlen; /* count of ra_runt */
};
static u32 __iptfs_get_inner_mtu(struct xfrm_state *x, int outer_mtu);
static enum hrtimer_restart iptfs_delay_timer(struct hrtimer *me);
+static enum hrtimer_restart iptfs_drop_timer(struct hrtimer *me);
/* ================= */
/* Utility Functions */
@@ -216,6 +228,63 @@ iptfs_pskb_extract_seq(u32 skblen, struct skb_seq_state *st, u32 off, int len)
return skb;
}
+/**
+ * iptfs_input_save_runt() - save data in xtfs runt space.
+ * @xtfs: xtfs state
+ * @seq: the current sequence
+ * @buf: packet data
+ * @len: length of packet data
+ *
+ * Save the small (`len`) start of a fragmented packet in `buf` in the xtfs data
+ * runt space.
+ */
+static void iptfs_input_save_runt(struct xfrm_iptfs_data *xtfs, u64 seq,
+ u8 *buf, int len)
+{
+ BUG_ON(xtfs->ra_newskb); /* we won't have a new SKB yet */
+
+ memcpy(xtfs->ra_runt, buf, len);
+
+ xtfs->ra_runtlen = len;
+ xtfs->ra_wantseq = seq + 1;
+}
+
+/**
+ * __iptfs_iphlen() - return the v4/v6 header length using packet data.
+ * @data: pointer at octet with version nibble
+ *
+ * The version data is expected to be valid (i.e., either 4 or 6).
+ */
+static u32 __iptfs_iphlen(u8 *data)
+{
+ struct iphdr *iph = (struct iphdr *)data;
+
+ if (iph->version == 0x4)
+ return sizeof(*iph);
+ BUG_ON(iph->version != 0x6);
+ return sizeof(struct ipv6hdr);
+}
+
+/**
+ * __iptfs_iplen() - return the v4/v6 length using packet data.
+ * @data: pointer to ip (v4/v6) packet header
+ *
+ * Grab the IPv4 or IPv6 length value in the start of the inner packet header
+ * pointed to by `data`. Assumes data len is enough for the length field only.
+ *
+ * The version data is expected to be valid (i.e., either 4 or 6).
+ */
+static u32 __iptfs_iplen(u8 *data)
+{
+ struct iphdr *iph = (struct iphdr *)data;
+
+ if (iph->version == 0x4)
+ return ntohs(iph->tot_len);
+ BUG_ON(iph->version != 0x6);
+ return ntohs(((struct ipv6hdr *)iph)->payload_len) +
+ sizeof(struct ipv6hdr);
+}
+
/**
* iptfs_complete_inner_skb() - finish preparing the inner packet for gro recv.
* @x: xfrm state
@@ -265,6 +334,238 @@ static void iptfs_complete_inner_skb(struct xfrm_state *x, struct sk_buff *skb)
}
}
+static void __iptfs_reassem_done(struct xfrm_iptfs_data *xtfs, bool free)
+{
+ assert_spin_locked(&xtfs->drop_lock);
+
+ /* We don't care if it works locking takes care of things */
+ hrtimer_try_to_cancel(&xtfs->drop_timer);
+ if (free)
+ kfree_skb(xtfs->ra_newskb);
+ xtfs->ra_newskb = NULL;
+}
+
+/**
+ * iptfs_reassem_abort() - In-progress packet is aborted free the state.
+ * @xtfs: xtfs state
+ */
+static void iptfs_reassem_abort(struct xfrm_iptfs_data *xtfs)
+{
+ __iptfs_reassem_done(xtfs, true);
+}
+
+/**
+ * iptfs_reassem_done() - In-progress packet is complete, clear the state.
+ * @xtfs: xtfs state
+ */
+static void iptfs_reassem_done(struct xfrm_iptfs_data *xtfs)
+{
+ __iptfs_reassem_done(xtfs, false);
+}
+
+/**
+ * iptfs_reassem_cont() - Continue the reassembly of an inner packets.
+ * @xtfs: xtfs state
+ * @seq: sequence of current packet
+ * @st: seq read stat for current packet
+ * @skb: current packet
+ * @data: offset into sequential packet data
+ * @blkoff: packet blkoff value
+ * @list: list of skbs to enqueue completed packet on
+ *
+ * Process an IPTFS payload that has a non-zero `blkoff` or when we are
+ * expecting the continuation b/c we have a runt or in-progress packet.
+ */
+static u32 iptfs_reassem_cont(struct xfrm_iptfs_data *xtfs, u64 seq,
+ struct skb_seq_state *st, struct sk_buff *skb,
+ u32 data, u32 blkoff, struct list_head *list)
+{
+ struct sk_buff *newskb = xtfs->ra_newskb;
+ u32 remaining = skb->len - data;
+ u32 runtlen = xtfs->ra_runtlen;
+ u32 copylen, fraglen, ipremain, iphlen, iphremain, rrem;
+
+ /* Handle packet fragment we aren't expecting */
+ if (!runtlen && !xtfs->ra_newskb)
+ return data + min(blkoff, remaining);
+
+ /* Important to remember that input to this function is an ordered
+ * packet stream (unless the user disabled the reorder window). Thus if
+ * we are waiting for, and expecting the next packet so we can continue
+ * assembly, a newer sequence number indicates older ones are not coming
+ * (or if they do should be ignored). Technically we can receive older
+ * ones when the reorder window is disabled; however, the user should
+ * have disabled fragmentation in this case, and regardless we don't
+ * deal with it.
+ *
+ * blkoff could be zero if the stream is messed up (or it's an all pad
+ * insertion) be careful to handle that case in each of the below
+ */
+
+ /* Too old case: This can happen when the reorder window is disabled so
+ * ordering isn't actually guaranteed.
+ */
+ if (seq < xtfs->ra_wantseq)
+ return data + remaining;
+
+ /* Too new case: We missed what we wanted cleanup. */
+ if (seq > xtfs->ra_wantseq) {
+ XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMINIPTFSERROR);
+ goto abandon;
+ }
+
+ if (blkoff == 0) {
+ if ((*skb->data & 0xF0) != 0) {
+ XFRM_INC_STATS(dev_net(skb->dev),
+ LINUX_MIB_XFRMINIPTFSERROR);
+ goto abandon;
+ }
+ /* Handle all pad case, advance expected sequence number.
+ * (RFC 9347 S2.2.3)
+ */
+ xtfs->ra_wantseq++;
+ /* will end parsing */
+ return data + remaining;
+ }
+
+ if (runtlen) {
+ BUG_ON(xtfs->ra_newskb);
+
+ /* Regardless of what happens we're done with the runt */
+ xtfs->ra_runtlen = 0;
+
+ /* The start of this inner packet was at the very end of the last
+ * iptfs payload which didn't include enough for the ip header
+ * length field. We must have *at least* that now.
+ */
+ rrem = sizeof(xtfs->ra_runt) - runtlen;
+ if (remaining < rrem || blkoff < rrem) {
+ XFRM_INC_STATS(dev_net(skb->dev),
+ LINUX_MIB_XFRMINIPTFSERROR);
+ goto abandon;
+ }
+
+ /* fill in the runt data */
+ if (skb_copy_bits_seq(st, data, &xtfs->ra_runt[runtlen],
+ rrem)) {
+ XFRM_INC_STATS(dev_net(skb->dev),
+ LINUX_MIB_XFRMINBUFFERERROR);
+ goto abandon;
+ }
+
+ /* We have enough data to get the ip length value now,
+ * allocate an in progress skb
+ */
+ ipremain = __iptfs_iplen(xtfs->ra_runt);
+ if (ipremain < sizeof(xtfs->ra_runt)) {
+ /* length has to be at least runtsize large */
+ XFRM_INC_STATS(dev_net(skb->dev),
+ LINUX_MIB_XFRMINIPTFSERROR);
+ goto abandon;
+ }
+
+ /* For the runt case we don't attempt sharing currently. NOTE:
+ * Currently, this IPTFS implementation will not create runts.
+ */
+
+ newskb = iptfs_alloc_skb(skb, ipremain, false);
+ if (!newskb) {
+ XFRM_INC_STATS(dev_net(skb->dev),
+ LINUX_MIB_XFRMINERROR);
+ goto abandon;
+ }
+ xtfs->ra_newskb = newskb;
+
+ /* Copy the runt data into the buffer, but leave data
+ * pointers the same as normal non-runt case. The extra `rrem`
+ * recopied bytes are basically cacheline free. Allows using
+ * same logic below to complete.
+ */
+ memcpy(skb_put(newskb, runtlen), xtfs->ra_runt,
+ sizeof(xtfs->ra_runt));
+ }
+
+ /* Continue reassembling the packet */
+ ipremain = __iptfs_iplen(newskb->data);
+ iphlen = __iptfs_iphlen(newskb->data);
+
+ /* Sanity check, we created the newskb knowing the IP length so the IP
+ * length can't now be shorter.
+ */
+ BUG_ON(newskb->len > ipremain);
+
+ ipremain -= newskb->len;
+ if (blkoff < ipremain) {
+ /* Corrupt data, we don't have enough to complete the packet */
+ XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMINIPTFSERROR);
+ goto abandon;
+ }
+
+ /* We want the IP header in linear space */
+ if (newskb->len < iphlen) {
+ iphremain = iphlen - newskb->len;
+ if (blkoff < iphremain) {
+ XFRM_INC_STATS(dev_net(skb->dev),
+ LINUX_MIB_XFRMINIPTFSERROR);
+ goto abandon;
+ }
+ fraglen = min(blkoff, remaining);
+ copylen = min(fraglen, iphremain);
+ BUG_ON(skb_tailroom(newskb) < copylen);
+ if (skb_copy_bits_seq(st, data, skb_put(newskb, copylen),
+ copylen)) {
+ XFRM_INC_STATS(dev_net(skb->dev),
+ LINUX_MIB_XFRMINBUFFERERROR);
+ goto abandon;
+ }
+ /* this is a silly condition that might occur anyway */
+ if (copylen < iphremain) {
+ xtfs->ra_wantseq++;
+ return data + fraglen;
+ }
+ /* update data and things derived from it */
+ data += copylen;
+ blkoff -= copylen;
+ remaining -= copylen;
+ ipremain -= copylen;
+ }
+
+ fraglen = min(blkoff, remaining);
+ copylen = min(fraglen, ipremain);
+
+ /* We verified this was true in the main receive routine */
+ BUG_ON(skb_tailroom(newskb) < copylen);
+
+ /* copy fragment data into newskb */
+ if (skb_copy_bits_seq(st, data, skb_put(newskb, copylen), copylen)) {
+ XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMINBUFFERERROR);
+ goto abandon;
+ }
+
+ if (copylen < ipremain) {
+ xtfs->ra_wantseq++;
+ } else {
+ /* We are done with packet reassembly! */
+ BUG_ON(copylen != ipremain);
+ iptfs_reassem_done(xtfs);
+ iptfs_complete_inner_skb(xtfs->x, newskb);
+ list_add_tail(&newskb->list, list);
+ }
+
+ /* will continue on to new data block or end */
+ return data + fraglen;
+
+abandon:
+ if (xtfs->ra_newskb) {
+ iptfs_reassem_abort(xtfs);
+ } else {
+ xtfs->ra_runtlen = 0;
+ xtfs->ra_wantseq = 0;
+ }
+ /* skip past fragment, maybe to end */
+ return data + min(blkoff, remaining);
+}
+
/**
* iptfs_input() - handle receipt of iptfs payload
* @x: xfrm state
@@ -285,7 +586,7 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
struct iphdr *iph;
struct net *net;
u32 remaining, iplen, iphlen, data, tail;
- u32 blkoff;
+ u32 blkoff, capturelen;
u64 seq;
xtfs = x->mode_data;
@@ -331,12 +632,27 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
INIT_LIST_HEAD(&sublist);
- /* Fragment handling in following commits */
+ /* Handle fragment at start of payload, and/or waiting reassembly. */
+
blkoff = ntohs(ipth->block_offset);
- data += blkoff;
+ /* check before locking i.e., maybe */
+ if (blkoff || xtfs->ra_runtlen || xtfs->ra_newskb) {
+ spin_lock(&xtfs->drop_lock);
+
+ /* check again after lock */
+ if (blkoff || xtfs->ra_runtlen || xtfs->ra_newskb) {
+ data = iptfs_reassem_cont(xtfs, seq, &skbseq, skb, data,
+ blkoff, &sublist);
+ }
+
+ spin_unlock(&xtfs->drop_lock);
+ }
/* New packets */
+
tail = skb->len;
+ BUG_ON(xtfs->ra_newskb && data < tail);
+
while (data < tail) {
__be16 protocol = 0;
@@ -355,8 +671,13 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
iph = (struct iphdr *)hbytes;
if (iph->version == 0x4) {
/* must have at least tot_len field present */
- if (remaining < 4)
+ if (remaining < 4) {
+ /* save the bytes we have, advance data and exit */
+ iptfs_input_save_runt(xtfs, seq, hbytes,
+ remaining);
+ data += remaining;
break;
+ }
iplen = be16_to_cpu(iph->tot_len);
iphlen = iph->ihl << 2;
@@ -364,8 +685,13 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
XFRM_MODE_SKB_CB(skbseq.root_skb)->tos = iph->tos;
} else if (iph->version == 0x6) {
/* must have at least payload_len field present */
- if (remaining < 6)
+ if (remaining < 6) {
+ /* save the bytes we have, advance data and exit */
+ iptfs_input_save_runt(xtfs, seq, hbytes,
+ remaining);
+ data += remaining;
break;
+ }
iplen = be16_to_cpu(
((struct ipv6hdr *)hbytes)->payload_len);
@@ -376,6 +702,7 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
ipv6_get_dsfield((struct ipv6hdr *)iph);
} else if (iph->version == 0x0) {
/* pad */
+ data = tail;
break;
} else {
XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR);
@@ -395,16 +722,14 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
if (!first_skb)
first_skb = skb;
- /* Fragment handling in following commits */
- if (iplen > remaining)
- break;
-
- skb = iptfs_pskb_extract_seq(iplen, &skbseq, data, iplen);
+ capturelen = min(iplen, remaining);
+ skb = iptfs_pskb_extract_seq(iplen, &skbseq, data, capturelen);
if (!skb) {
/* skip to next packet or done */
- data += iplen;
+ data += capturelen;
continue;
}
+ BUG_ON(skb->len != capturelen);
skb->protocol = protocol;
if (old_mac) {
@@ -415,11 +740,38 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
eth_hdr(skb)->h_proto = skb->protocol;
}
- data += iplen;
+ data += capturelen;
+
+ if (skb->len < iplen) {
+ BUG_ON(data != tail);
+ BUG_ON(xtfs->ra_newskb);
+
+ /* Start reassembly */
+ spin_lock(&xtfs->drop_lock);
+
+ xtfs->ra_newskb = skb;
+ xtfs->ra_wantseq = seq + 1;
+ if (!hrtimer_is_queued(&xtfs->drop_timer)) {
+ /* softirq blocked lest the timer fire and interrupt us */
+ BUG_ON(!in_interrupt());
+ hrtimer_start(&xtfs->drop_timer,
+ xtfs->drop_time_ns,
+ IPTFS_HRTIMER_MODE);
+ }
+
+ spin_unlock(&xtfs->drop_lock);
+
+ break;
+ }
+
iptfs_complete_inner_skb(x, skb);
list_add_tail(&skb->list, &sublist);
}
+ if (data != tail)
+ /* this should not happen from the above code */
+ XFRM_INC_STATS(dev_net(skb->dev), LINUX_MIB_XFRMINIPTFSERROR);
+
/* Send the packets! */
list_for_each_entry_safe(skb, next, &sublist, list) {
skb_list_del_init(skb);
@@ -447,6 +799,45 @@ static int iptfs_input(struct xfrm_state *x, struct sk_buff *skb)
return -EINPROGRESS;
}
+/**
+ * iptfs_drop_timer() - Handle drop timer expiry.
+ * @me: the timer
+ *
+ * This is similar to our input function.
+ *
+ * The drop timer is set when we start an in progress reassembly, and also when
+ * we save a future packet in the window saved array.
+ *
+ * NOTE packets in the save window are always newer WRT drop times as
+ * they get further in the future. i.e. for:
+ *
+ * if slots (S0, S1, ... Sn) and `Dn` is the drop time for slot `Sn`,
+ * then D(n-1) <= D(n).
+ *
+ * So, regardless of why the timer is firing we can always discard any inprogress
+ * fragment; either it's the reassembly timer, or slot 0 is going to be
+ * dropped as S0 must have the most recent drop time, and slot 0 holds the
+ * continuation fragment of the in progress packet.
+ */
+static enum hrtimer_restart iptfs_drop_timer(struct hrtimer *me)
+{
+ struct xfrm_iptfs_data *xtfs;
+ struct xfrm_state *x;
+
+ xtfs = container_of(me, typeof(*xtfs), drop_timer);
+ x = xtfs->x;
+
+ /* Drop any in progress packet */
+ spin_lock(&xtfs->drop_lock);
+ if (xtfs->ra_newskb) {
+ kfree_skb(xtfs->ra_newskb);
+ xtfs->ra_newskb = NULL;
+ }
+ spin_unlock(&xtfs->drop_lock);
+
+ return HRTIMER_NORESTART;
+}
+
/* ================================= */
/* IPTFS Sending (ingress) Functions */
/* ================================= */
@@ -1251,6 +1642,8 @@ static int iptfs_user_init(struct net *net, struct xfrm_state *x,
xc->max_queue_size = net->xfrm.sysctl_iptfs_max_qsize;
xtfs->init_delay_ns =
(u64)net->xfrm.sysctl_iptfs_init_delay * NSECS_IN_USEC;
+ xtfs->drop_time_ns =
+ (u64)net->xfrm.sysctl_iptfs_drop_time * NSECS_IN_USEC;
if (attrs[XFRMA_IPTFS_DONT_FRAG])
xc->dont_frag = true;
@@ -1268,6 +1661,10 @@ static int iptfs_user_init(struct net *net, struct xfrm_state *x,
}
if (attrs[XFRMA_IPTFS_MAX_QSIZE])
xc->max_queue_size = nla_get_u32(attrs[XFRMA_IPTFS_MAX_QSIZE]);
+ if (attrs[XFRMA_IPTFS_DROP_TIME])
+ xtfs->drop_time_ns =
+ (u64)nla_get_u32(attrs[XFRMA_IPTFS_DROP_TIME]) *
+ NSECS_IN_USEC;
if (attrs[XFRMA_IPTFS_INIT_DELAY])
xtfs->init_delay_ns =
(u64)nla_get_u32(attrs[XFRMA_IPTFS_INIT_DELAY]) *
@@ -1306,7 +1703,9 @@ static int iptfs_copy_to_user(struct xfrm_state *x, struct sk_buff *skb)
u64 q;
if (x->dir == XFRM_SA_DIR_IN) {
- ret = nla_put_u32(skb, XFRMA_IPTFS_DROP_TIME, 0);
+ q = xtfs->drop_time_ns;
+ (void)do_div(q, NSECS_IN_USEC);
+ ret = nla_put_u32(skb, XFRMA_IPTFS_DROP_TIME, q);
if (ret)
return ret;
@@ -1342,6 +1741,10 @@ static int __iptfs_init_state(struct xfrm_state *x,
hrtimer_init(&xtfs->iptfs_timer, CLOCK_MONOTONIC, IPTFS_HRTIMER_MODE);
xtfs->iptfs_timer.function = iptfs_delay_timer;
+ spin_lock_init(&xtfs->drop_lock);
+ hrtimer_init(&xtfs->drop_timer, CLOCK_MONOTONIC, IPTFS_HRTIMER_MODE);
+ xtfs->drop_timer.function = iptfs_drop_timer;
+
/* Modify type (esp) adjustment values */
if (x->props.family == AF_INET)
@@ -1369,6 +1772,8 @@ static int iptfs_clone(struct xfrm_state *x, struct xfrm_state *orig)
if (!xtfs)
return -ENOMEM;
+ xtfs->ra_newskb = NULL;
+
err = __iptfs_init_state(x, xtfs);
if (err)
return err;
@@ -1399,7 +1804,14 @@ static void iptfs_delete_state(struct xfrm_state *x)
if (!xtfs)
return;
+ spin_lock_bh(&xtfs->drop_lock);
hrtimer_cancel(&xtfs->iptfs_timer);
+ hrtimer_cancel(&xtfs->drop_timer);
+ spin_unlock_bh(&xtfs->drop_lock);
+
+ if (xtfs->ra_newskb)
+ kfree_skb(xtfs->ra_newskb);
+
kfree_sensitive(xtfs);
module_put(x->mode_cbs->owner);
--
2.45.2
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