phxsqlproxy 在GetDBNameFromReqBuf调用中产生core dump

[loveleon]

gdb core文件，发现在
void IOChannel::GetDBNameFromReqBuf(const char * buf, int buf_size) {
if (buf_size > 5) {
char cmd = buf[4];
if (cmd == COM_INIT_DB) {
int buf_len = 0;
memcpy(&buf_len, buf, 3);
db_name_ = std::string(buf + 5, buf_len - 1);
LOG_DEBUG("bufsize %d buflen %d ret [%s]", buf_size, buf_len, db_name_.c_str());
}
}
}
构造db_name_值时候，堆栈如下：
(gdb) bt
#0 __memcpy_sse2_unaligned () at ../sysdeps/x86_64/multiarch/memcpy-sse2-unaligned.S:84
#1 0x0000000000415e12 in std::string::_S_construct<char const*> (
__beg=0x7f6d77197ef5 "\003\335xxt\0\036J_A_ORG_HIS_MAX_USED_LIMIT_PCTsq\0~\0\034\0\0\0\003sq\0~\0\037", '\377' <repeats 11 times>, "\376\377\377\377\376\0\0\0\001uq\0~\0\"\0\0\0\002\004xxxt\0\033J_FIRST_LOANCARD_OPEN_MONTHt\0\a2015.09t\0\021J_A_PMT_M3_CNT_18q\0~\0\030t\0\020J_LBL_IS_ACCFUNDq\0~\0"..., __end=0x7f6d7775af50 "", __a=...)
at /usr/include/c++/4.8/bits/basic_string.tcc:140
#2 0x00000000005bc3ed in std::basic_string<char, std::char_traits, std::allocator >::basic_string(char const*, unsigned long, std::allocator const&) ()
#3 0x0000000000413ebe in phxsqlproxy::IOChannel::GetDBNameFromReqBuf (this=0x12ac0f0,
buf=0x7f6d77197ef0 "\0\0\002\003\335xxt\0\036J_A_ORG_HIS_MAX_USED_LIMIT_PCTsq\0~\0\034\0\0\0\003sq\0~\0\037", '\377' <repeats 11 times>, "\376\377\377\377\376\0\0\0\001uq\0~\0\"\0\0\0\002\004xxxt\0\033J_FIRST_LOANCARD_OPEN_MONTHt\0\a2015.09t\0\021J_A_PMT_M3_CNT_18q\0~\0\030t\0\020J_LBL_IS_ACCFUNDq"..., buf_size=16384) at io_channel.cpp:268
#4 0x000000000041392e in phxsqlproxy::IOChannel::TransMsgDirect (this=0x12ac0f0, source_fd=109, dest_fd=112, pf=0x7f6d7719bf70, nfds=2) at io_channel.cpp:178
#5 0x0000000000413495 in phxsqlproxy::IOChannel::TransMsg (this=0x12ac0f0, client_fd=109, sqlsvr_fd=112) at io_channel.cpp:107
#6 0x0000000000410b8d in phxsqlproxy::IORoutine::run (this=0x12ac060) at io_routine.cpp:161
#7 0x0000000000416efd in phxsqlproxy::RoutineRun (p=0x12ac060) at phxcoroutine.cpp:35
#8 0x0000000000438c13 in CoRoutineFunc (co=0x7f6de40d1530) at co_routine.cpp:440
#9 0x0000000000000000 in ?? ()
请问，在IOChannel::TransMsgDirect 函数中，定义char buf[1024*16],然后POLLIN中，
if ((read_once = read(source_fd, buf, sizeof(buf))) <= 0) { 中，能否确保读到一个完整的mysql报文。这里的逻辑处理，是否导致了底层数据读取出错？或是mysql client端协议与mysql server5.6版本不同导致？

[loveleon]

在frame 3中，
(gdb) p/x buf[0]
$1 = 0x5c
(gdb) p/x buf[1]
$2 = 0x30
(gdb) p/x buf[2]
$3 = 0x5c
(gdb)

[loveleon]

mysql 字段为longblob时候，如果发送数据包长度，超过16k。read_once操作读取包就不会是完整报文。