lwn.git/net/ipv4/tcp_output.c, branch v3.4.14

tcp: Apply device TSO segment limit earlier

2012-10-02T17:29:34+00:00

[ Upstream commit 1485348d2424e1131ea42efc033cbd9366462b01 ] Cache the device gso_max_segs in sock::sk_gso_max_segs and use it to limit the size of TSO skbs. This avoids the need to fall back to software GSO for local TCP senders. Signed-off-by: Ben Hutchings Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tcp: fix retransmit of partially acked frames

2012-04-18T20:52:45+00:00

Alexander Beregalov reported skb_over_panic errors and provided stack trace. I occurs commit a21d45726aca (tcp: avoid order-1 allocations on wifi and tx path) added a regression, when a retransmit is done after a partial ACK. tcp_retransmit_skb() tries to aggregate several frames if the first one has enough available room to hold the following ones payload. This is controlled by /proc/sys/net/ipv4/tcp_retrans_collapse tunable (default : enabled) Problem is we must make sure _pskb_trim_head() doesnt fool skb_availroom() when pulling some bytes from skb (this pull is done when receiver ACK part of the frame). Reported-by: Alexander Beregalov Cc: Marc MERLIN Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: avoid order-1 allocations on wifi and tx path

2012-04-11T14:11:12+00:00

Marc Merlin reported many order-1 allocations failures in TX path on its wireless setup, that dont make any sense with MTU=1500 network, and non SG capable hardware. After investigation, it turns out TCP uses sk_stream_alloc_skb() and used as a convention skb_tailroom(skb) to know how many bytes of data payload could be put in this skb (for non SG capable devices) Note : these skb used kmalloc-4096 (MTU=1500 + MAX_HEADER + sizeof(struct skb_shared_info) being above 2048) Later, mac80211 layer need to add some bytes at the tail of skb (IEEE80211_ENCRYPT_TAILROOM = 18 bytes) and since no more tailroom is available has to call pskb_expand_head() and request order-1 allocations. This patch changes sk_stream_alloc_skb() so that only sk->sk_prot->max_header bytes of headroom are reserved, and use a new skb field, avail_size to hold the data payload limit. This way, order-0 allocations done by TCP stack can leave more than 2 KB of tailroom and no more allocation is performed in mac80211 layer (or any layer needing some tailroom) avail_size is unioned with mark/dropcount, since mark will be set later in IP stack for output packets. Therefore, skb size is unchanged. Reported-by: Marc MERLIN Tested-by: Marc MERLIN Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2012-02-04T21:39:32+00:00

tcp: fix tcp_trim_head() to adjust segment count with skb MSS

2012-01-30T17:42:58+00:00

This commit fixes tcp_trim_head() to recalculate the number of segments in the skb with the skb's existing MSS, so trimming the head causes the skb segment count to be monotonically non-increasing - it should stay the same or go down, but not increase. Previously tcp_trim_head() used the current MSS of the connection. But if there was a decrease in MSS between original transmission and ACK (e.g. due to PMTUD), this could cause tcp_trim_head() to counter-intuitively increase the segment count when trimming bytes off the head of an skb. This violated assumptions in tcp_tso_acked() that tcp_trim_head() only decreases the packet count, so that packets_acked in tcp_tso_acked() could underflow, leading tcp_clean_rtx_queue() to pass u32 pkts_acked values as large as 0xffffffff to ca_ops->pkts_acked(). As an aside, if tcp_trim_head() had really wanted the skb to reflect the current MSS, it should have called tcp_set_skb_tso_segs() unconditionally, since a decrease in MSS would mean that a single-packet skb should now be sliced into multiple segments. Signed-off-by: Neal Cardwell Acked-by: Nandita Dukkipati Acked-by: Ilpo Järvinen Signed-off-by: David S. Miller

tcp: add LINUX_MIB_TCPRETRANSFAIL counter

2012-01-26T18:51:00+00:00

It might be useful to get a counter of failed tcp_retransmit_skb() calls. Reported-by: Satoru Moriya Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

foundations of per-cgroup memory pressure controlling.

2011-12-13T00:04:10+00:00

This patch replaces all uses of struct sock fields' memory_pressure, memory_allocated, sockets_allocated, and sysctl_mem to acessor macros. Those macros can either receive a socket argument, or a mem_cgroup argument, depending on the context they live in. Since we're only doing a macro wrapping here, no performance impact at all is expected in the case where we don't have cgroups disabled. Signed-off-by: Glauber Costa Reviewed-by: Hiroyouki Kamezawa CC: David S. Miller CC: Eric W. Biederman CC: Eric Dumazet Signed-off-by: David S. Miller

tcp: fix tcp_trim_head()

2011-12-05T23:30:03+00:00

commit f07d960df3 (tcp: avoid frag allocation for small frames) breaked assumption in tcp stack that skb is either linear (skb->data_len == 0), or fully fragged (skb->data_len == skb->len) tcp_trim_head() made this assumption, we must fix it. Thanks to Vijay for providing a very detailed explanation. Reported-by: Vijay Subramanian Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: take care of misalignments

2011-12-04T18:20:39+00:00

We discovered that TCP stack could retransmit misaligned skbs if a malicious peer acknowledged sub MSS frame. This currently can happen only if output interface is non SG enabled : If SG is enabled, tcp builds headless skbs (all payload is included in fragments), so the tcp trimming process only removes parts of skb fragments, header stay aligned. Some arches cant handle misalignments, so force a head reallocation and shrink headroom to MAX_TCP_HEADER. Dont care about misaligments on x86 and PPC (or other arches setting NET_IP_ALIGN to 0) This patch introduces __pskb_copy() which can specify the headroom of new head, and pskb_copy() becomes a wrapper on top of __pskb_copy() Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: do not scale TSO segment size with reordering degree

2011-11-29T05:29:41+00:00

Since 2005 (c1b4a7e69576d65efc31a8cea0714173c2841244) tcp_tso_should_defer has been using tcp_max_burst() as a target limit for deciding how large to make outgoing TSO packets when not using sysctl_tcp_tso_win_divisor. But since 2008 (dd9e0dda66ba38a2ddd1405ac279894260dc5c36) tcp_max_burst() returns the reordering degree. We should not have tcp_tso_should_defer attempt to build larger segments just because there is more reordering. This commit splits the notion of deferral size used in TSO from the notion of burst size used in cwnd moderation, and returns the TSO deferral limit to its original value. Signed-off-by: Neal Cardwell Signed-off-by: David S. Miller