commit 8015ba0c4a9333967059bdf7c302f7a71e5ec5ea
Author: Christopher Faulet <cfaulet@haproxy.com>
Date:   Mon Jan 6 11:37:00 2020 +0100

    BUG/MINOR: proxy: Fix input data copy when an error is captured
    
    In proxy_capture_error(), input data are copied in the error snapshot. The copy
    must take care of the data wrapping. But the length of the first block is
    wrong. It should be the amount of contiguous input data that can be copied
    starting from the input's beginning. But the mininum between the input length
    and the buffer size minus the input length is used instead. So it is a problem
    if input data are wrapping or if more than the half of the buffer is used by
    input data.
    
    This patch must be backported as far as 1.9.
    
    (cherry picked from commit 47a7210b9d377d91777f39241fab54d5f83b2728)
    Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

diff --git a/src/proxy.c b/src/proxy.c
index 1abd6654f..2d02b1b5d 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -1546,7 +1546,7 @@ void proxy_capture_error(struct proxy *proxy, int is_back,
 	es->buf_len = buf_len;
 	es->ev_id   = ev_id;
 
-	len1 = b_size(buf) - buf_len;
+	len1 = b_size(buf) - b_peek_ofs(buf, buf_out);
 	if (len1 > buf_len)
 		len1 = buf_len;