Mercurial > hg > nginx
view src/event/quic/bpf/ngx_quic_reuseport_helper.c @ 9300:5be23505292b default tip
SSI: fixed incorrect or duplicate stub output.
Following 3518:eb3aaf8bd2a9 (0.8.37), r->request_output is only set
if there are data in the first buffer sent in the subrequest. As a
result, following the change mentioned this flag cannot be used to
prevent duplicate ngx_http_ssi_stub_output() calls, since it is not
set if there was already some output, but the first buffer was empty.
Still, when there are multiple subrequests, even an empty subrequest
response might be delayed by the postpone filter, leading to a second
call of ngx_http_ssi_stub_output() during finalization from
ngx_http_writer() the subreqest buffers are released by the postpone
filter. Since r->request_output is not set after the first call, this
resulted in duplicate stub output.
Additionally, checking only the first buffer might be wrong in some
unusual cases. For example, the first buffer might be empty if
$r->flush() is called before printing any data in the embedded Perl
module.
Depending on the postpone_output value and corresponding sizes, this
issue can result in either duplicate or unexpected stub output, or
"zero size buf in writer" alerts.
Following 8124:f5515e727656 (1.23.4), it became slightly easier to
reproduce the issue, as empty static files and empty cache items now
result in a response with an empty buffer. Before the change, an empty
proxied response can be used to reproduce the issue.
Fix is check all buffers and set r->request_output if any non-empty
buffers are sent. This ensures that all unusual cases of non-empty
responses are covered, and also that r->request_output will be set
after the first stub output, preventing duplicate output.
Reported by Jan Gassen.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Thu, 04 Jul 2024 17:41:28 +0300 |
parents | a2fbae359828 |
children |
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line source
#include <errno.h> #include <linux/string.h> #include <linux/udp.h> #include <linux/bpf.h> /* * the bpf_helpers.h is not included into linux-headers, only available * with kernel sources in "tools/lib/bpf/bpf_helpers.h" or in libbpf. */ #include <bpf/bpf_helpers.h> #if !defined(SEC) #define SEC(NAME) __attribute__((section(NAME), used)) #endif #if defined(LICENSE_GPL) /* * To see debug: * * echo 1 > /sys/kernel/debug/tracing/events/bpf_trace/enable * cat /sys/kernel/debug/tracing/trace_pipe * echo 0 > /sys/kernel/debug/tracing/events/bpf_trace/enable */ #define debugmsg(fmt, ...) \ do { \ char __buf[] = fmt; \ bpf_trace_printk(__buf, sizeof(__buf), ##__VA_ARGS__); \ } while (0) #else #define debugmsg(fmt, ...) #endif char _license[] SEC("license") = LICENSE; /*****************************************************************************/ #define NGX_QUIC_PKT_LONG 0x80 /* header form */ #define NGX_QUIC_SERVER_CID_LEN 20 #define advance_data(nbytes) \ offset += nbytes; \ if (start + offset > end) { \ debugmsg("cannot read %ld bytes at offset %ld", nbytes, offset); \ goto failed; \ } \ data = start + offset - 1; #define ngx_quic_parse_uint64(p) \ (((__u64)(p)[0] << 56) | \ ((__u64)(p)[1] << 48) | \ ((__u64)(p)[2] << 40) | \ ((__u64)(p)[3] << 32) | \ ((__u64)(p)[4] << 24) | \ ((__u64)(p)[5] << 16) | \ ((__u64)(p)[6] << 8) | \ ((__u64)(p)[7])) /* * actual map object is created by the "bpf" system call, * all pointers to this variable are replaced by the bpf loader */ struct bpf_map_def SEC("maps") ngx_quic_sockmap; SEC(PROGNAME) int ngx_quic_select_socket_by_dcid(struct sk_reuseport_md *ctx) { int rc; __u64 key; size_t len, offset; unsigned char *start, *end, *data, *dcid; start = ctx->data; end = (unsigned char *) ctx->data_end; offset = 0; advance_data(sizeof(struct udphdr)); /* data at UDP header */ advance_data(1); /* data at QUIC flags */ if (data[0] & NGX_QUIC_PKT_LONG) { advance_data(4); /* data at QUIC version */ advance_data(1); /* data at DCID len */ len = data[0]; /* read DCID length */ if (len < 8) { /* it's useless to search for key in such short DCID */ return SK_PASS; } } else { len = NGX_QUIC_SERVER_CID_LEN; } dcid = &data[1]; advance_data(len); /* we expect the packet to have full DCID */ /* make verifier happy */ if (dcid + sizeof(__u64) > end) { goto failed; } key = ngx_quic_parse_uint64(dcid); rc = bpf_sk_select_reuseport(ctx, &ngx_quic_sockmap, &key, 0); switch (rc) { case 0: debugmsg("nginx quic socket selected by key 0x%llx", key); return SK_PASS; /* kernel returns positive error numbers, errno.h defines positive */ case -ENOENT: debugmsg("nginx quic default route for key 0x%llx", key); /* let the default reuseport logic decide which socket to choose */ return SK_PASS; default: debugmsg("nginx quic bpf_sk_select_reuseport err: %d key 0x%llx", rc, key); goto failed; } failed: /* * SK_DROP will generate ICMP, but we may want to process "invalid" packet * in userspace quic to investigate further and finally react properly * (maybe ignore, maybe send something in response or close connection) */ return SK_PASS; }